Solid electrolytic moldings, electrode moldings, and electrochemical elements including a polybutadiene block copolymer

ABSTRACT

Disclosed are a molded solid electrolyte and molded electrode having excellent electrochemical properties and high procesability. As a binder for these molded articles, a hydrogenated block copolymer is used which is obtained by hydrogenating a straight chain or branched block copolymer containing a block (A) comprising polybutadiene whose 1,2-vinyl bond content is 15% or less and a block (B) comprising a butadiene (co)polymer consisting of 50 to 100% by weight of butadiene and 0 to 50% by weight of other monomers in which 1,2-vinyl bond content of butadiene portion is 20 to 90%, wherein (A)/(B)=5 to 70/95 to 30% by weight.

TECHNICAL FIELD

The present invention relates to electrochemical devices, and moldedsolid electrolytes and molded electrodes used in the electrochemicaldevices. More particularly, the present invention relates to moldedarticles holding therein an electrolyte material and electrode materialby adding a polymer compound to these electrochemical deviceconstituting materials, and an electrochemical device fabricated usingthese molded articles.

BACKGROUND ART

Electrochemical devices such as battery cells comprise an electrolytelayer where ion transfer takes place and an electrode layer whereelectron transfers to ions takes place together with the ion transfer.Polymer compounds are added to the electrolyte layer and electrode layerfor the following purposes.

1) Addition to the Electrolyte Layer

Since electrolytes are usually liquid with a supporting salt dissolvedin a solvent, and hence require a container for containing the liquid,electrochemical devices using such electrolytes are difficult to makesmaller and thinner. To solve this problem, researches are beingconducted on all-solid state electrochemical devices using solidelectrolytes in place of traditional liquid electrolytes.

Among others, lithium batteries have been researched vigorously as thetype of battery that can obtain high energy density since lithium is asubstance with a light atomic weight and large ionization energy, andnowadays, lithium batteries are extensively used as power sources forportable appliances.

On the other hand, with the widespread use of lithium batteries, concernhas been growing in recent years about the safety of batteries becauseof increased internal energy associated with the increase in the amountof active material content and also because of increasing amounts oforganic solvents which are flammable materials used as electrolytes.

As a method to ensure the safety of lithium batteries, it is extremelyeffective to use solid electrolytes, which are nonflammable, in place oforganic solvent electrolytes. It is therefore important to use solidelectrolytes for lithium batteries in order to ensure high safety levelsas well as to achieve the earlier noted small and thin construction.

Materials such as lithium halide, lithium nitride, lithium oxygen acidsalt, or their derivatives, are known as materials for lithium ionconductive solid electrolytes used in such batteries. Amorphous solidelectrolytes of lithium ion conductive sulfides such as Li₂S-SiS₂,Li₂S-P₂S₅, Li₂S-B₂S₃, and the like, and lithium ion conductive solidelectrolytes formed from such glasses doped with a lithium halide suchas LiI or a lithium salt such as Li₃PO₄, are known to exhibit high ionicconductivity of the order of 10⁻⁴ to 10⁻³ S/cm or higher.

As compared with these inorganic solid electrolytes, a polymer solidelectrolyte comprising an organic substance is obtained from a solutionof a lithium salt and an organic polymer compound by allowing thesolvent to evaporate. This polymer solid electrolyte has excellentworkability compared with inorganic solid electrolytes, in that it canbe easily formed into a thin film and in that the resulting solidelectrolyte thin film has flexibility.

As a solid electrolyte having flexibility or rubber elasticity, therehas recently been proposed a novel solid electrolyte, named the “polymerin salts” electrolyte, that comprises an inorganic salt and a polymerand has lithium ion conductivity of extremely high density compared withthe above-described polymer solid electrolyte (C. A. Angell, C. Liu, andE. Sanchez, Nature, vol. 362, (1993) 137).

In electrochemical devices using liquid electrolytes also, a porouspolymer compound is usually used as a separator in the electrolytelayer. The separator may mechanically prevent an electrical contactbetween the electrodes, and is required not only to have excellentliquid retentivity for retaining the liquid electrolyte and bechemically stable in the electrochemical device, but also to beelectrochemically stable since it is used in contact with theelectrodes.

2) Addition to the Electrode Layer

An electrode is formed by molding an electrode active material andcontacting the same with a current collector. If the electrode activematerial is simply molded by a pressure molding process, the cohesiveforce working between electrode active material particles primarilydepends only on van der Waals forces. However, since conventionalelectrochemical devices use liquid as the electrolyte, if the moldedelectrode formed by the pressure molding process alone is immersed inthe liquid electrolyte, liquid molecules are adsorbed onto the surfacesof the electrode active material particles, as a result of which thecohesive force working between the active material particles decreasesand active material particles drop off the molded electrode into theliquid electrolyte, resulting in that the shape of the molded electrodecannot be retained. To increase the formability of the electrode,usually a polymer compound is added as a binding agent to the moldedelectrode.

To the electrolyte layer or electrode layer of an electrochemicaldevice, polymer compounds are added for the above-described purposes,but the prior art techniques have had the following problems.

The inorganic solid electrolytes described above are ceramic or glass,and in battery cell applications, the materials are usually used in theform of pellets obtained by pressure molding pulverized solidelectrolyte powder. However, since the pellets are hard and brittle,there has been the problem that they lack workability and are difficultto be made thin.

The organic solid electrolytes, on the other hand, have low ionicconductivity of the order of 10⁻⁴ S/cm or less at room temperature,which has not been sufficient for practical lithium cell electrolytes.To solve this problem, it has been proposed to make a polymer solidelectrolyte with increased ionic conductivity by adding a plasticizer.However, plasticizers are flammable by their nature, and the addition ofa plasticizer in turn gives rise to such problems as decreased lithiumion transport number or decreased reactivity with the lithium anode.Furthermore, whether a plasticizer is added or not, it is hard to saythat these organic solid electrolytes have sufficient performance aslithium battery electrolytes.

Further, most of the solid electrolytes generally known as the “polymerin salt” electrolyte have low ionic conductivity, of the order of 10⁻⁴S/cm or less, which cannot be said to be sufficient for lithium batteryelectrolytes. If an ambient temperature molten salt such asAlCl₃-LiBr-LiClO₄ is used as the inorganic salt, high ionic conductivitycan be obtained, but this in turn tends to cause an electrochemicalreduction of aluminum and, therefore, cannot be said to be suitable forlithium cell electrolytes.

As earlier described, the molded electrode is constituted by a mixture,which is prepared by mixing a polymer compound as a binder into theelectrode active material. The polymer compound is usually anelectrically insulating substance and tends to interfere with the iontransfer, thus interfering with the electrochemical reaction occurringat the electrode/electrolyte interface and also the dispersion of ionswithin the electrode. If the mixing ratio of the polymer compound isincreased to improve the formability, there arises the problem that theoperating characteristics of the electrochemical device tend to drop.

Further, the molded electrode is formed by mixing in a dispersing mediuma mixture comprising an electrode active material, a binder, and anelectron conductive material added if necessary to increase the electronconductivity within the electrode, and by loading or coating a currentcollector with the resulting slurry and allowing the dispersing mediumto evaporate. To enhance the coating or loading properties of theslurry, it is desirable that the polymer compound used as the binder besoluble in the dispersing medium used.

When a solid electrolyte is used as the electrolyte, particles of theelectrode active material are prevented from being separated anddropping into the electrolyte. However, in that case also, if the moldedelectrode is formed by simply pressure molding an electrode activematerial, or a mixture of an electrode active material and a solidelectrolyte to increase the reacting surface area, the molded electrodeis hard and brittle and lacks workability, the resulting problem beingdifficulty in constructing the electrochemical device.

Further, when a solid electrolyte is used as the electrolyte, since thecontact interface with the electrode active material is a solid/solidinterface, the contact surface area between the electrode activematerial and the electrolyte becomes smaller than when a liquidelectrolyte is used. This therefore, tends to increase the electrodereaction resistance. When an electrically insulating polymer compound isadded to improve the formability, this tendency becomes more pronounced.This has therefore led to the problem that the electrode reaction speedtends to drop.

Taking the lithium battery as an example of the electrochemical device,lithiated cobalt oxide (Li_(x)CoO₂) or the like is used as the cathodeactive material, and graphite or the like as the anode active material.Since these materials are obtained as powder, if they are simplypressure molded into molded electrodes for use in the lithium battery,as earlier described, the liquid electrolyte penetrates between theelectrode constituent particles, causing the electrodes to swell andthus resulting in the problem that not only does it become difficult toretain the shape but the electrical contact also tends to be lost.

Further, Li_(x)CoO₂ has a structure of a triangular lattice of oxygen,lithium, and cobalt stacked in the order of O, Li, O, Co, O, Li, and O,and lithium ions are accommodated between the CoO₂ layers. Through anelectrochemical oxidation reduction reaction within the lithium ionconductive electrolyte, the lithium ions move in and out the spacebetween the CoO₂ layers. As a result, the degree of electricalinteraction between the CoO₂ layers varies, causing the layer spacing toexpand and contract and hence a volumetric change of the electrode. Thishas lead to the problem that as charge/discharge cycles are repeated,bonds between the electrode forming particles tend to be lost and thecapacity drops with charge/discharge cycles.

The above description has been given by taking Li_(x)CoO₂ as an exampleof the electrode active material; materials traditionally used as thelithium cell active materials or materials expected to be used in thefuture include transition metal oxides such as Li_(x)NiO₂, Li_(x)MnO₂,MnO₂ and the like, transition metal disulfides such as Li_(x)TiS₂ andthe like, graphite intercalation compounds, and graphite fluorides.Similar problems can arise with these materials.

Further, when a solid electrolyte is used as the electrolyte, thecontact area between the solid electrolyte and the electrode activematerial tends to decrease, as earlier noted. Accordingly, when avolumetric change occurs in the electrode active material in associationwith the charge and discharge operations of the cell, bonds between theactive material and the electrolyte tend to be lost. Moreover, sincecell materials are all formed from solid substances, and there are noelastic members for absorbing the volumetric change of the electrodeactive material during charging and discharging, a dimensional changemay occur in the cell, leading to sealing failure of cell seals.

An object of the present invention is to provide a molded solidelectrolyte that solves the above enumerated problems, and that exhibitsexcellent electrochemical properties such as high ionic conductivity andhas flexibility and hence excellent workability.

Another object of the present invention is to provide a molded electrodethat permits the construction of an electrochemical device havingexcellent operating characteristics, and that has excellent formabilityand workability.

Still another object of the present invention is to provide anelectrochemical device that shows stable operation by resolving theproblems associated with the volumetric change of the electrode activematerial occurring during the operation of the electrochemical device.

DISCLOSURE OF THE INVENTION

The molded solid electrolyte of the present invention comprises a solidelectrolyte and a hydrogenated block copolymer obtained by hydrogenatinga straight chain or branched block copolymer; the straight chain orbranched block copolymer containing a block (A) comprising polybutadienewhose 1,2-vinyl bond content is 15% or less and a block (B) comprising abutadiene (co)polymer consisting of 50 to 100% by weight of butadieneand 0 to 50% by weight of other monomers and in which 1,2-vinyl bondcontent of the butadiene is 20 to 90%, wherein (A)/(B)=5 to 70/95 to 30%by weight.

The molded electrode of the present invention comprises an electrodeactive material and the hydrogenated block copolymer described above.

The electrochemical device of the present invention comprises a pair ofelectrodes and an electrolyte layer, wherein at least either the pair ofelectrodes or the electrolyte layer contains the hydrogenated blockcopolymer described above.

The hydrogenated block copolymer, one of the primary components of thepresent invention, is a hydrogenated block copolymer obtained byhydrogenating 90% or more of a straight chain or branched block polymer(hereinafter called the unhydrogenated block polymer) which contains atleast one polybutadiene block (A) (hereinafter called the block A) whose1,2-vinyl bond content is 15% or less and at least one butadiene(co)polymer (hereinafter called the block B) which consists of 50 to100% by weight of butadiene and 0 to 50% by weight of other monomers andin which the 1,2-vinyl bond content of the butadiene is 20 to 90%,wherein the ratio between the block A and block B in the molecules is 5to 70/95 to 30 (% by weight).

In the hydrogenated block polymer, by hydrogenation the block A becomesa crystalline polyethylene-like structural block and the block B becomesa rubber-like block with olefin skeleton.

Here, as the solid electrolyte of the molded solid electrolyte, alithium ion conductive solid electrolyte is used.

Further, an amorphous solid electrolyte is used as the solidelectrolyte.

As the lithium ion amorphous solid electrolyte, an electrolyte composedprimarily of a sulfide, and particularly, an electrolyte containingsilicon, is preferably used.

The molded solid electrolyte can also contain an electronicallyinsulating structural member.

Preferably, the molded electrode contains a lithium ion conductiveinorganic solid electrolyte.

As the lithium ion conductive inorganic solid electrolyte, an amorphouselectrolyte composed primarily of a sulfide is preferably used.

Preferably, the molded electrode contains a structural member, and morepreferably, the structural member is electron conductive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view showing in simplified form theconstruction of an apparatus for evaluating the electrochemicalproperties of a molded electrode in one example of the presentinvention.

FIG. 2 is a diagram showing AC impedance spectra for the moldedelectrodes of the same example and a comparative example.

FIG. 3 is a vertical cross sectional view showing in simplified form theconstruction of an apparatus for evaluating the electrochemicalproperties of a molded electrode in another example of the presentinvention.

FIG. 4 is a diagram showing AC impedance spectra for the moldedelectrodes of the same example and comparative examples.

FIG. 5 is a vertical cross sectional view of a lithium cell according tostill another example of the present invention.

FIG. 6 is a diagram showing the charge/discharge cycle characteristicsof the lithium cells of the same example and a comparative example.

FIG. 7 is a vertical cross sectional view of an all-solid lithium cellaccording to yet another example of the present invention.

FIG. 8 is a diagram showing the charge/discharge cycle characteristicsof the all-solid lithium cells of the same example and comparativeexamples.

FIG. 9 is a vertical cross sectional view of a display electrode of anelectroluminescent display device according to a further example of thepresent invention.

FIG. 10 is a vertical cross sectional view of the display device.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is based on the findings of the present inventorsthat by using as a polymer compound a hydrogenated block copolymerhaving a crystalline polyethylene-like structural block and an olefinskeleton rubber-like block, the ion transfer between substancesconstituting an electrochemical device, for example, between inorganicsolid electrolyte particles, between electrode active materialparticles, or across the interface between the electrode active materialand the electrolyte, is facilitated and high formability and flexibilitycan be given to a molded solid electrolyte, a molded electrode and thelike, to improve their workability.

For example, if a polymer compound is mixed to give flexibility to aninorganic solid electrolyte, the surfaces of the inorganic solidelectrolyte particles would be covered with the insulating polymercompound. As the result, ionic conduction between the solid electrolyteparticles is interfered, and the ionic conductivity of the resultingcomplex of the ion conductive inorganic solid electrolyte and thepolymer compound would decrease. However, if the hydrogenated blockcopolymer having a crystalline polyethylene-like structural block and arubber-like block with olefin network according to the present inventionis used as the polymer compound, the bonding between the solidelectrolyte particles can be increased without appreciably impairing thehigh ionic conductivity and flexibility and the like are given to themolded solid electrolyte.

The hydrogenated block copolymer according to the present invention, byintroducing the crystalline polyethylene-like structural blockthereinto, can give flexibility even in a small amount and a lithium ionconductive molded article having high conductivity can be obtained.

The present invention will be described in detail below.

The 1,2-vinyl bond content in block A before hydrogenation is animportant factor that determines the melting point attributed to theblock A and the cohesive force between the polyethylene-like structuralblocks after hydrogenation. In particular, if the cohesive force drops,it becomes impossible to reduce the amount to be added, and a lithiumion conductive complex having high conductivity cannot be obtained.

The 1,2-vinyl bond content in the block A must be 15% or less. If the1,2-vinyl bond content in the block A exceeds 15%, the cohesive force ofthe block A after hydrogenation decreases, which is undesirable, and themelting point also drops, which is also undesirable.

Block B before hydrogenation is a block segment comprising a butadiene(co)polymer which consists of 50 to 100% by weight of butadiene and 0 to50% by weight of other monomers, with the 1,2-vinyl bond content of thebutadiene being 20 to 90%, and becomes a rubber-like block byhydrogenation.

In the block B, since the 1,2-vinyl bond of the butadiene becomes abutene structure by hydrogenation, the content directly influences theglass transition temperature attributed to the block B afterhydrogenation and, in the complex with the lithium ion conductive solidelectrolyte, becomes a factor that influences flexibility.

In the present invention, the 1,2-vinyl bond content in the block B mustbe 20% or higher but not exceed 90%. If the 1,2-vinyl bond content inthe block B is less than 20%, crystalline parts occur afterhydrogenation and flexibility decreases, which is not desirable. Onthe-other hand, if it exceeds 90%, the butene content increasesexcessively to raise the glass transition temperature; this decreasesthe flexibility and is not desirable.

As other monomers copolymerizable with the butadiene in the block B,there are aromatic vinyl compounds such as styrene, α-methyl styrene andpara-methyl styrene, (meth)acrylate esters such as methyl methacrylateand methyl acrylate, and isoprene and the like; of these, styrene andisoprene are particularly preferable.

The amount of these monomers used is 0 to 50% of all the monomersconstituting the block B. When these monomers are used, if the amount ofother monomers used exceeds 50%, flexibility after hydrogenation drops,which is not desirable. Further, the block copolymer beforehydrogenation may include a polymer block (hereinafter referred to asthe block X) composed primarily of an aromatic vinyl compound.

The hydrogenated block copolymer of the present invention is ahydrogenated block copolymer obtained by hydrogenating a straight chainor branched block copolymer containing at least one block A, at leastone block B, and, if necessary, block X.

The unhydrogenated block copolymer is, to be specific, a copolymerexpressed by the structural formula A-(B-A)_(l), (A-B)_(m) wherein l andm are 1 or larger or (A-B-X)_(n) wherein n is 1 or larger.

Among block copolymers having such a structure, a tri-block copolymer ofA-B-A or a tri-block copolymer of A-B-X wherein X is a polystyrene blockis preferable.

The ratio of the block A to the block B in the unhydrogenated blockcopolymer is block A/Block B=5 to 70/95 to 30% by weight.

If the block A in the unhydrogenated block copolymer is less than 5% byweight with the block B exceeding 95% by weight, the crystalline blocksegment is not sufficient and the cohesive force decreases; as theresult, high formability cannot be obtained in a range where the addingamount is small. If the block A exceeds 70% by weight with the block Bless than 30% by weight, the hardness of the hydrogenated blockcopolymer increases and flexibility is lost.

In the case of the unhydrogenated block copolymer of (A-B-X)_(n), theratio of the block X in the unhydrogenated block copolymer is usually50% by weight or less, preferably 40% by weight or less, and morepreferably 30% by weight or less.

If the block X exceeds 50% by weight, the flexibility of thehydrogenated block copolymer decreases and hence, the flexibility of themolded solid electrolyte decreases. Here also, it is desirable that theratio of the block A to the block B be held within the earlier notedrange, in the portion excluding the block X.

The percentage of the hydrogen added to the block copolymer, afterhydrogenation, must be 90% or higher. If the percentage of thehydrogenation is less than 90%, the melting point drops and the heatresistance decreases.

The hydrogenated block copolymer has the characteristic of exhibitingthe melting point attributed to the block A after hydrogenation at ahigher temperature side and the glass transition point attributed to theblock B after hydrogenation at a lower temperature side.

The melting point of the hydrogenated block copolymer is a factor thatdirectly affects the heat resistance of the composition of the presentinvention, and is usually 80° C. or higher, preferably 85° C. or higher,and particularly preferably 95° C. or higher. If the melting point islower than 80° C., the heat resistance of the composition is not enoughand poses a problem in practical use. In conventional electrochemicaldevices, an upper limit to the operating temperature range of the deviceis imposed by the boiling point of the electrolyte used; in the case ofan electrochemical device using a solid electrolyte as the electrolyte,the upper limit of the operating temperature range becomes higher.Further, since an activation energy of the conduction of a solidelectrolyte is generally higher than that of a liquid electrolyte, iontransfer at higher speed at a higher temperature in the electrolyte and,therefore, electrochemical devices using solid electrolytes exhibitsuperior properties at high temperature to those of devices using liquidelectrolytes. Accordingly, it is required that the polymer compound usedhave high heat resistance. Further, in the case of a fuel cell or thelike using a proton conducting solid electrolyte, the temperature of thedevice can rise close to 100° C. because of the heat generated duringdevice operation. It is, therefore, more preferable that the meltingpoint of the hydrogenated block copolymer is 95° C. or higher.

The glass transition temperature at a lower temperature side of thehydrogenated block copolymer, on the other hand, is a factor thataffects the low temperature characteristics of the composition, and isusually −25° C. or lower, preferably −30° C. or lower, and particularlypreferably −35° C. or lower. If the glass transition temperature at alower temperature side is higher than −25° C., dynamic properties at lowtemperatures degrade, and also the ionic conductivity at a lowertemperature side of the composition decreases significantly.

The hydrogenated block copolymer can be produced by using knowntechniques. For example, the method disclosed in Japanese PatentUnexamined Publication No. 4-342752 can be used.

As solid electrolytes so far found to exhibit ionic conductivity of 10⁻⁴S/cm or higher at room temperature, there have been found solidelectrolytes of copper ion conductive, silver ion conductive, protonconducting, and fluoride ion conductive and the like. Among others, thelithium ion conductive solid electrolyte has been attracting attentionas an electrolyte for all-solid lithium cells. However, lithium cellswhich generate high voltage comprise a cathode that exhibits a strongoxidizing power and an anode that exhibits a strong reducing power.Therefore, even if the polymer compound added to the electrolyte layerexhibits the characteristic that does not interfere with ion transferand that provides a high binding property, deterioration may occurthrough contact with the cathode or anode. However, the hydrogenatedblock copolymer of the present invention is stable to such oxidationreduction reactions and, thus, offers the greatest effect when used witha lithium ion conductive solid electrolyte for the construction of amolded solid electrolyte.

The kinds of the solid electrolyte, for example in the case of lithiumion conductive electrolytes, may be divided into the crystalline typesuch as Li_(1.3)Sc_(0.3)Ti_(1.7)(PO₄)₃ and Li_(0.2)La_(0.6)TiO₃, and theamorphous type such as Li₂S-SiS₂. Many crystalline solid electrolytesshow anisotropy to ionic conductivity, and in order to realize a highionic conductivity, it often becomes necessary to sinter the moldedarticle and connect ion conductive paths between solid electrolyteparticles. On the other hand, amorphous solid electrolytes show isotropyto ionic conductivity, and ion conductive paths between particles can beeasily connected by a pressure molding process. It is thereforepreferable to use an amorphous solid electrolyte for a molded solidelectrolyte if it is intended to simplify the process of electrochemicaldevice fabrication.

Lithium ion conductive amorphous solid electrolytes include thoseconsisting essentially sulfides such as Li₂S-SiS₂, and those consistingessentially oxides such as Li₂S-SiO₂. Electrolytes consisting primarilyof sulfides have high reactivity with moisture and the like, and thereis a need to use a nonpolar solvent when mixing with a polymer compound.The hydrogenated block copolymer of the present invention is soluble ina nonpolar solvent, and can form a complex without impairing theproperties of lithium ion conductive amorphous solid electrolytesconsisting essentially sulfides.

For lithium ion conductive inorganic solid electrolytes, those having ahigh ionic conductivity and wide potential window are preferable, andamorphous electrolytes consisting primarily of sulfides, which possessboth of these characteristics, are particularly preferable.

For lithium ion conductive amorphous inorganic solid electrolytes, if alithium sulfide and a silicon sulfide are used as starting materials,evaporation of the starting materials can be suppressed whensynthesizing the solid electrolyte, since the vapor pressure of thestarting materials is low. This serves to simplify the process of solidelectrolyte synthesis; therefore, for lithium ion conductive amorphousinorganic compounds, those containing silicon are particularlypreferable for use.

Further, by adding an electronically insulating structural member, themechanical strength of the lithium ion conductive molded solidelectrolyte can be further increased.

For specific examples of the electronically insulating structuralmember, there are a woven fabric, non-woven fabric, porous film, and thelike.

In a method of producing the molded solid electrolyte of the presentinvention, a hydrogenated block copolymer solution is added to solidelectrolyte powder and, then, mixed and dispersed using a paintconditioner or the like to obtain a slurry with the solid electrolytepowder dispersed through the hydrogenated block copolymer solution.Next, the slurry is applied onto a substrate having releasing propertyto obtain a film-like molded solid electrolyte; alternatively, theslurry is applied to or impregnated into an electronically insulatingstructural member such as a woven fabric to obtain a sheet-like moldedsolid electrolyte.

The hydrogenated block copolymer of the present invention, whencomplexed with other particles, does not interfere with ion transfer,provides good inter-particle bonding, and permits the production of amolded article having high workability. Further, in the electrodes usedin an electrochemical device, ions are transferred between the electrodeactive material and the electrolyte. As previously noted, highformability must be given to the electrodes without interfering with theion transfer; therefore, by using the hydrogenated block copolymer ofthe present invention, a molded electrode that can satisfy theserequirements can be produced.

Furthermore, when a solid electrolyte is used as the electrolyte, if abinder is added to improve the formability, the electrode reaction speedtends to drop, which is a problem as previously noted; therefore, usingthe hydrogenated block copolymer as the binder is particularlyeffective.

Moreover, for the active material used as the electrode active materialin lithium cells, the oxidation reduction resistance of the binder isimportant, as previously stated; for this reason also, using thehydrogenated block copolymer is particularly effective. In that case,the molded electrode contains the electrode active material or theelectrode active material and solid electrolyte, and the solidelectrolyte used is of the lithium ion conductive type.

For the lithium ion conductive solid electrolyte, the amorphous type ispreferable, since it does not have anisotropy with respect to ionconductive paths and thus makes it easy to connect ion conductive pathsbetween the electrode active material and the electrolyte. For theamorphous lithium ion conductive solid electrolyte, an electrolyteconsisting essentially of a sulfide is particularly preferable for use,since such an electrolyte exhibits a high ionic conductivity and widepotential window.

Further, by adding a structural member to the molded electrode, themechanical strength of the molded electrode can be further increased. Astructural member formed from an electron conductive material isparticularly preferable for use, since such a structure serves toincrease the electron conductivity within the electrode. Examples of theelectron conductive structural member that can be used here are ametallic mesh and the like formed from stainless steel, titanium,copper, and the like.

The hydrogenated block copolymer used in the present invention containsa rubber-like block with olefin skeleton as well as a crystallinepolyethylene-like structural block. The rubber-like block with olefinskeleton has a large free volume, and can therefore absorb thevolumetric change of the electrode active material occurring during theoperation of the electrochemical device. Further, since the crystallinepolyethylene-like structural block provides strong bonding andflexibility between the constituent particles of the electrochemicaldevice, problems associated with the decreased inter-particle bondingdue to the volumetric change of the active material can be resolved, andan electrochemical device that is stable in operation can thus beachieved.

The present invention will be described in detail below by way ofexample.

The synthesis of lithium ion conductive inorganic solid electrolytes andthe measurement of their ion conductivity hereinafter described were allconducted in a dry argon atmosphere.

First, synthesizing examples of hydrogenated block copolymers will bedescribed. In Table 1, the structures and properties of the hydrogenatedblock copolymers are shown. In the table, A, B, and X in the componentstructural formula represents the block A, block B, and polystyreneblock, respectively.

Methods of their production are shown below.

1) Production of the Hydrogenated Block Copolymer (H-1) 3.2 kg ofcyclohexane and 1.2 kg of butadiene are introduced into an autoclavewith a net capacity of 20 liters, and 33 ml of a 14% by weighttetrahydrofuran solution of n-butyl lithium is added. The mixture isheated to about 70° C., and when the percentage of addition reaches100%, 2.8 kg of butadiene and 108 ml of tetrahydrofuran are furtheradded, and the polymerization is continued at about 70° C. When thepercentage of addition reaches 100%, 26 ml of a 20% by weighttetrahydrofuran solution of dicyclosilane is added, and is allowed toreact for about 20 minutes, thereby coupling diblock polymers to obtaina triblock copolymer. After the completion of the polymerization, thereaction solution is maintained at about 70° C., and 3 g of n-butyllithium, 3 g of 2,6-di-t-butyl-p-cresol, 1 g ofbis(cyclopentadienyl)titanium dichloride, and 2 g of diethylaluminumchloride are added, and are allowed to react for one hour under ahydrogen pressure of 10 kg/cm². After stream stripping, the reactionliquid is dried on rolls, to obtain the hydrogenated block copolymer(H-1).

2) Production of the Hydrogenated Block Copolymers (H-2) to (H-4)

Similarly to the production of the hydrogenated block copolymer (H-1),the hydrogenated block copolymers (H-2) to (H-4) are obtained by varyingthe monomer combination, monomer amounts, catalyst amounts,polymerization temperature, polymerization time and the like to give thehydrogenated block copolymer produced as shown in Table 1.

TABLE 1 Sample number H-1 H-2 H-3 H-4 Component structural A-B-A A-B-AA-B-A A-B-X formula 1,2-vinyl bond content (%) 12 13 12 13 in block AAmount of block A (% by 30 20 40 15 weight) (15 × 2) (10 × 2) (20 × 2)1,2-vinyl bond content (%) 42 41 65 42 in block B Amount of block B (%by 70 80 60 70 weight) Amount of block X (% by 15 weight) PropertiesPercentage of 98 97 98.5 97.5 hydrogenation (%) Melting point (at higher92 89 90 92 temperature side) Glass transition −52 −54 −55 −51temperature (at lower temperature side) MFR (230° C. × 2.16 kg) 10 5 80.5 Molecular weight (× 10⁴⁾ 15 20 15 15

EXAMPLE 1

A lithium ion conductive molded solid electrolyte was obtained by usinga lithium ion conductive glass sulfide represented by 0.6Li₂S-0.4SiS₂ asthe solid electrolyte and (H-1) as the hydrogenated block copolymer. Thedetails are shown below.

First, as the solid electrolyte, the lithium ion conductive amorphoussolid electrolyte represented by 0.6Li₂S-0.4SiS₂ was synthesized in thefollowing manner.

Lithium sulfide (Li₂S) and silicon sulfide (SiS₂) were mixed at a ratioof 0.6:0.4 by mole, and the mixture was introduced into a glass-likecarbon crucible. The crucible was then placed in a vertical furnace andheated up to 950° C. in an argon stream to melt the mixture. Afterheating for two hours, the crucible was dropped into liquid nitrogen forrapid cooling, to obtain the lithium ion conductive amorphous solidelectrolyte represented by 0.6Li₂S-0.4SiS₂.

Using the thus obtained lithium ion conductive amorphous solidelectrolyte and the hydrogenated block copolymer (H-1), the lithium ionconductive molded solid electrolyte was produced in the followingmanner.

First, the solid electrolyte obtained in the above process waspulverized to 350 mesh or finer powder. To the solid electrolyte powder,a toluene solution of (H-1) was then added, and thoroughly kneaded toobtain a slurry. The mixing ratio, when kneading, was chosen such thatthe solid content of the hydrogenated block copolymer to the solidelectrolyte powder was 2:98 by weight. The thus obtained slurry wasapplied onto a fluorocarbon resin plate by a doctor blade method, andwas dried by allowing the toluene to evaporate under a reduced pressureat 100° C. After drying for three hours, by separating from thefluorocarbon resin plate, the lithium ion conductive molded solidelectrolyte was obtained.

The ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured by the AC impedance method described below.

First, the lithium ion conductive molded solid electrolyte sheetobtained in the above process was cut out into the shape of a disk witha diameter of 10 mm. Then, a 10-mm diameter platinum plate as impedancemeasuring electrode was adhered by pressure onto each side of the diskto form an ionic conductivity measuring cell.

The AC impedance was measured by applying an AC voltage of 10 mV using avector impedance analyzer. As the result, the ionic conductivity of thelithium ion conductive molded solid electrolyte thus measured was2.45×10⁻⁴ S/cm.

As a comparative example, the solid electrolyte powder was pressuremolded without adding the hydrogenated block copolymer, and when theionic conductivity was measured in the same manner, the result showed4.5×10⁻⁴ S/cm.

Next, to examine the flexibility of the lithium ion conductive moldedsolid electrolyte for the evaluation of workability, a bending test wasconducted. The bending test was carried out by winding the lithium ionconductive molded solid electrolyte around a 50-mm diameter stainlesssteel rod and visually inspecting the condition of the molded article.The result showed that no externally discernible faults were observed onthe lithium ion conductive molded solid electrolyte of this example,thus demonstrating that the molded article had high flexibility evev inthe bending test.

As described above, it has been found that, according to the presentinvention, a lithium ion conductive molded solid electrolyte having ahigh lithium ion conductivity and excellent workability can be obtained.

EXAMPLE 2

Except that (H-1) used as the hydrogenated block copolymer in EXAMPLE 1was replaced by (H-2), a lithium ion conductive molded solid electrolytewas obtained in the same manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured in the same manner as in EXAMPLE 1, the resultshowed 2.8×10⁻⁴ S/cm.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 3

Except that (H-1) used as the hydrogenated block copolymer in EXAMPLE 1was replaced by (H-3), a lithium ion conductive molded solid electrolytewas obtained in the same manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured in the same manner as in EXAMPLE 1 the resultshowed 3.4×10⁻⁴ S/cm.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 4

Except that (H-1) used as the hydrogenated block copolymer in EXAMPLE 1was replaced by (H-4), a lithium ion conductive molded solid electrolytewas obtained in the same manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured in the same manner as in EXAMPLE 1, the resultshowed 2.5×10⁻⁴ S/cm.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 5

A lithium ion conductive molded solid electrolyte was produced by usinga lithium ion conductive amorphous solid electrolyte represented by0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ as the lithium ion conductive inorganicsolid electrolyte and, as in EXAMPLE 3, (H-3) as the hydrogenated blockcopolymer. The details are shown below.

First, as the lithium ion conductive inorganic solid electrolyte, thelithium ion conductive amorphous solid electrolyte represented by0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ was synthesized in the following manner.

First, a glass matrix for synthesizing the amorphous solid electrolytewas synthesized. Lithium sulfide (Li₂S) and silicon sulfide (SiS₂) weremixed at a ratio of 0.64:0.36 by mole, and the mixture was introducedinto a glass-like carbon crucible and melted at 950° C. in a horizontalfurnace. After that, the molten liquid was rapidly cooled on a twinroller, to obtain an amorphous solid electrolyte represented by0.64Li₂S-0.36SiS₂. This amorphous solid electrolyte as the glass matrixwas pulverized, and lithium phosphate was mixed into the powder so as toprovide the composition 0.01Li₃PO₄-0.63Li₂S-0.36SiS₂. This mixture washeated and then rapidly cooled in the same manner as above, to obtainthe lithium ion conductive amorphous solid electrolyte represented by0.01Li₃PO₄-0.63Li₂S-0.36SiS₂.

Except that the solid electrolyte obtained in the above process was usedin place of the solid electrolyte represented by 0.6Li₂S-0.4SiS₂ andthat (H-3) used in EXAMPLE 3 was used as the hydrogenated blockcopolymer, the lithium ion conductive molded solid electrolyte was thenobtained in the same manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured in the same manner as in EXAMPLE 1, the resultshowed 5.3×10⁻⁴ S/cm. As a comparative example, when the ionicconductivity of the solid electrolyte powder itself was measured in thesame manner as in EXAMPLE 1, the result showed 7.8×10⁻⁴ S/cm.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 6

By using a lithium ion conductive amorphous solid electrolyterepresented by 0.05Li₂O-0.60Li₂S-0.35SiS₂ as the lithium ion conductiveinorganic solid electrolyte and, as in EXAMPLE 3, (H-3) as thehydrogenated block copolymer, a lithium ion conductive molded solidelectrolyte was produced. The details are shown below.

The lithium ion conductive amorphous solid electrolyte represented by0.05Li₂O-0.60Li₂S-0.35SiS₂ was synthesized in the same manner as inEXAMPLE 5, except that lithium oxide was used in place of lithiumphosphate.

Except that the lithium ion conductive solid electrolyte obtained in theabove process was used, and that (H-3) used in EXAMPLE 3 was used as thehydrogenated block copolymer, the lithium ion conductive molded solidelectrolyte was obtained in the same manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured in the same manner as in EXAMPLE 1, the resultshowed 4.3×10⁻⁴ S/cm. As a comparative example, when the ionicconductivity of the solid electrolyte powder itself was measured in thesame manner as in EXAMPLE 1, the result showed 6.6×10⁻⁴ S/cm.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 7

A lithium ion conductive molded solid electrolyte was produced by usinga lithium ion conductive amorphous solid electrolyte represented by0.30LiI-0.35Li₂S-0.35SiS₂ as the lithium ion conductive inorganic solidelectrolyte and, as in EXAMPLE 1, (H-1) as the hydrogenated blockcopolymer. The details are shown below.

To begin with, as the lithium ion conductive inorganic solidelectrolyte, the lithium ion conductive amorphous solid electrolyterepresented by 0.30LiI-0.35Li₂S-0.35SiS₂ was synthesized in thefollowing manner.

First, except that the mixing ratio of the starting materials wasvaried, an amorphous solid electrolyte represented by 0.5Li₂S-0.5SiS₂was obtained in the same manner as in EXAMPLE 1. This amorphous solidelectrolyte as a glass matrix was pulverized, and lithium iodide wasmixed into the powder so as to provide the composition0.30LiI-0.35Li₂S-0.35SiS₂. This mixture was again heated and rapidlycooled in like manner, to obtain the lithium ion conductive amorphoussolid electrolyte represented by 0.30LiI-0.35Li₂S-0.35SiS₂.

Except that the solid electrolyte obtained in the above process was usedin place of the solid electrolyte represented by 0.6Li₂S-0.4SiS₂, thelithium ion conductive molded solid electrolyte was then obtained in thesame manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte was measured in the same manner as in EXAMPLE 1, the resultshowed 3.5×10⁻⁴ S/cm. As a comparative example, when the ionicconductivity of the solid electrolyte powder itself was measured in thesame manner as in EXAMPLE 1, the result showed 7.2×10⁻⁴ S/cm.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 8

A lithium ion conductive molded solid electrolyte was produced by usinga lithium ion conductive amorphous solid electrolyte represented by0.5Li₂S-0.5P₂S₅ as the lithium ion conductive inorganic solidelectrolyte and, as in EXAMPLE 1, (H-1) as the hydrogenated blockcopolymer. The details are shown below.

First, as raw materials for the solid electrolyte, lithium sulfide(Li₂S) and phosphorus sulfide (P₂S₅) were mixed at a ratio of 0.5:0.5 bymole. The mixture was then sealed within a silica tube and melted at900° C., after which the silica tube was immersed into water for rapidcooling, to obtain the amorphous solid electrolyte represented by0.5Li₂S-0.5P₂S₅.

Except that the solid electrolyte obtained in the above process was usedin place of the solid electrolyte represented by 0.6Li₂S-0.4SiS₂, thelithium ion conductive molded solid electrolyte was then obtained in thesame manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte and that of the solid electrolyte powder as a comparativeexample were measured in the same manner as in EXAMPLE 1, the resultsshowed that the ionic conductivity of the molded solid electrolyte withthe hydrogenated block copolymer added thereto was 1.0×10⁻⁴ S/cm, ascompared with 1.6×10⁻⁴ S/cm for the solid electrolyte itself, the rateof decrease thus being held within one half.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 9

A lithium ion conductive molded solid electrolyte was produced by usinga lithium ion conductive amorphous solid electrolyte represented by0.6Li₂S-0.4B₂S₃ as the lithium ion conductive inorganic solidelectrolyte and, as in EXAMPLE 1, (H-1) as the hydrogenated blockcopolymer. The details are shown below.

First, except that lithium sulfide (Li₂S) and boron sulfide (B₂S₃) mixedat a ratio of 0.6:0.4 by mole were used as the raw materials for thesolid electrolyte, the amorphous solid electrolyte represented by0.6Li₂S-0.4B₂S₃ was obtained in the same manner as in EXAMPLE 8.

Except that the solid electrolyte obtained in the above process was usedin place of the solid electrolyte represented by 0.6Li₂S-0.4SiSB₂, thelithium ion conductive molded solid electrolyte was then obtained in thesame manner as in EXAMPLE 1.

When the ionic conductivity of the lithium ion conductive molded solidelectrolyte and that of the solid electrolyte powder as a comparativeexample were measured in the same manner as in EXAMPLE 1, the resultsshowed that the ionic conductivity of the molded solid electrolyte withthe hydrogenated block copolymer added thereto was 1.2×10⁻⁴ S/cm, ascompared with 1.9×10⁻⁴ S/cm for the solid electrolyte itself, the rateof decrease thus being held within one half.

Further, in the bending test conducted in the same manner as in EXAMPLE1, no externally discernible faults were observed, thus demonstratingthat the electrolyte had high flexibility.

EXAMPLE 10

Using an amorphous solid electrolyte represented by 0.6Li₂S-0.4SiS₂ asthe lithium ion inorganic solid electrolyte, as in EXAMPLE 1, and using(H-3) as the hydrogenated block copolymer, various lithium ionconductive molded solid electrolytes were obtained by varying thecomposition ratio between the lithium ion conductive inorganic solidelectrolyte and the hydrogenated block copolymer. The details are shownbelow.

Using the lithium ion conductive inorganic solid electrolyte obtained inEXAMPLE 1 and (H-3), lithium ion conductive molded solid electrolyteswith varying composition ratios were obtained by the same method as usedin EXAMPLE 1.

Table 2 shows the composition ratio versus ionic conductivityrelationships of the various lithium ion conductive molded solidelectrolytes. Table 2 also shows the results of the bending test.

TABLE 2 Ratio of 0.4 1.0 2.0 3.5 5.0 copolymer (% by weight) Ratio ofsolid 99.6  99.0  98.0  96.5  95.0  electrolyte (% by weight) Ionic 4.13.8 3.4 2.8 2.0 conductivity (× 10⁻⁴S/cm) Bendding test Good Good GoodGood Good Remarks Example 3

From the above results, it can be seen that by using the hydrogenatedblock copolymer in only small amounts, a lithium ion conductive moldedsolid electrolyte can be obtained that has excellent flexibility as wellas a very high ionic conductivity. The hydrogenated block copolymer hasthe characteristic that even if it is added in relatively large amounts,the decrease in the ionic conductivity is small.

EXAMPLE 11

A lithium ion conductive molded solid electrolyte was obtained by usingthe amorphous solid electrolyte represented by0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ obtained in EXAMPLE 5 as the lithium ionconductive inorganic solid electrolyte, and (H-3) as the hydrogenatedblock copolymer, and also using a polyethylene mesh as theelectronically insulating structural member. The details are shownbelow.

The slurry containing the solid electrolyte and designated polymers wasobtained in the same manner as in EXAMPLE 1. Next, using a doctor blademethod, the slurry was charged into the openings in a polyethylene meshhaving a porosity of 70%. After that, by drying the mesh by evaporatingthe toluene under a reduced pressure at 40° C., thus obtaining thelithium ion conductive molded solid electrolyte.

The ionic conductivity of the lithium ion conductive molded solidelectrolyte, when measured in the same manner as in EXAMPLE 1, was3.0×10⁻⁴ S/cm.

In the bending test conducted in the same manner as in EXAMPLE 1, noexternally discernible faults were observed, and also, in the bendingtest conducted using a 5-mm diameter stainless steel rod, no faults wereobserved, thus demonstrating that the lithium ion conductor according tothis example had high flexibility.

As described above, it has been found that a lithium ion conductivemolded solid electrolyte having particularly high workability as well asa high lithium ion conductivity can be obtained according to the presentinvention using a lithium ion conductive inorganic solid electrolyte, ahydrogenated block copolymer, and an electronically insulatingstructural member.

EXAMPLE 12

Except that the 0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ used as the lithium ionconductive inorganic solid electrolyte in EXAMPLE 11 was replaced by thelithium ion conductive amorphous solid electrolyte represented by0.6Li₂S-0.4SiS₂ obtained in EXAMPLE 1, that (H-3) used as thehydrogenated block copolymer in EXAMPLE 11 was replaced by (H-1), andthat the polyethylene mesh used as the electronically insulatingstructural member in EXAMPLE 11 was replaced by a glass fiber mesh, alithium ion conductive molded solid electrolyte was produced in the samemanner as in EXAMPLE 11.

The ionic conductivity of the resulting lithium ion conductive moldedsolid electrolyte, when measured in the same manner as in EXAMPLE 1, was3.3×10⁻⁴ S/cm.

In the bending test conducted in the same manner as in EXAMPLE 1, noexternally discernible faults were observed, and also, in the bendingtest conducted using a 5-mm diameter stainless steel rod, no faults wereobserved, thus demonstrating that the lithium ion conductive moldedsolid electrolyte according to this example had high flexibility.

Comparative Example 1

Using a styrene-ethylene-butylene-styrene block copolymer (KRATON G1652manufactured by SHELL, hereinafter designated SEBS) having nocrystalline block structures, and using, as in EXAMPLE 1, an amorphoussolid electrolyte represented by 0.6Li₂S-0.4SiS₂ as the lithium ionconductive inorganic solid electrolyte, various lithium ion conductivemolded solid electrolytes were obtained by varying the composition ratioof the lithium ion conductive inorganic solid electrolyte and the SEBS.The details are shown below.

Using the SEBS and the lithium ion conductive inorganic solidelectrolyte obtained in EXAMPLE 1, lithium ion conductive molded solidelectrolytes with varying composition ratios were obtained by the samemethod as used in EXAMPLE 1.

Table 3 shows the composition ratio versus ionic conductivityrelationships of the various lithium ion conductive molded solidelectrolytes. Table 3 also shows the results of the bending test.

TABLE 3 Ratio of  0.4  1.0  2.0  3.5  5.0 copolymer (% by weight) Ratioof solid 99.6 99.0 98.0 96.5 95.0 electrolyte (% by weight) Ionic — — — 0.9  0.5 conductivity (× 10⁻⁴S/cm) Bendding test Unable Unable UnableCracks Good to to to developed recover recover recover as a as a as amolded molded molded article article article Remarks Unable to recoveras a molded article; hence unable to measure conductivity

Comparative Example 2

Using a copolymer (hereinafter designated H-SBR) obtained byhydrogenating a styrene-butadiene random copolymer, which was producedby polymerizing 5% by weight of styrene and 95% by weight of butadiene,with the 1,2-vinyl bond content of the butadiene being 80%, and using,as in EXAMPLE 1, an amorphous solid electrolyte represented by0.6Li₂S-0.4SiS₂ as the lithium ion inorganic solid electrolyte, variouslithium ion conductive molded solid electrolytes were obtained byvarying the composition ratio between the lithium ion conductiveinorganic solid electrolyte and the H-SBR. The details are shown below.

Using the H-SBR and the lithium ion conductive inorganic solidelectrolyte obtained in EXAMPLE 1, lithium ion conductive molded solidelectrolytes with varying composition ratios were obtained by the samemethod as used in EXAMPLE 1.

Table 4 shows the composition ratio versus ionic conductivityrelationships of the various lithium ion conductive molded solidelectrolytes. Table 4 also shows the results of the bending test.

TABLE 4 Ratio of H-SBR  0.4  1.0  2.0  3.5  5.0 (% by weight) Ratio ofsolid 99.6 99.0 98.0 96.5 95.0 electrolyte (% by weight) Ionic — — — — 0.4 conductivity (× 10⁻⁴S/cm) Bendding test Unable Unable Unable UnableGood to to to to recover recover recover recover as a as a as a as amolded molded molded molded article article article article RemarksUnable to recover as a molded article; hence unable to measureconductivity

From the comparison between the EXAMPLES and the COMPARATIVE EXAMPLES,it can be seen that the hydrogenated block copolymer of the presentinvention having a crystalline block provides good workability andexcellent flexibility and is a suitable material for obtaining a lithiumion conductive molded solid electrolyte having a high ionicconductivity.

EXAMPLE 13

In this example, a proton conducting molded solid electrolyte wasproduced by using silica gel doped with phosphoric acid as the protonconducting solid electrolyte and (H-1) as the hydrogenated blockcopolymer.

First, silica gel doped with phosphoric acid was synthesized in thefollowing manner.

Tetraethoxysilane (hereinafter designated TEOS) was used as the startingmaterial for synthesizing the silica gel, and was diluted with ethanol.Here, the mixing ratio of the TEOS to the ethanol was chosen to be 1:4by mole. To this solution were added eight parts of pure water and 0.01parts of tetraethylammonium tetrafluoroborate, the parts being by molewith respect to the TEOS, and was further added an aqueous solution of3.6% by weight hydrochloric acid, with HCl being 0.01 parts by mole withrespect to the TEOS, and the resulting mixture was stirred for fiveminutes. After that, an aqueous solution of 85% by weight phosphoricacid was added with the ratio TEOS:H₃PO₄=1:0.5, and the mixture wasstirred in a hermetic container for three hours. The mixture was thenleft on stand for five hours for gelation, and heated for two hours at150° C., to obtain the phosphoric acid doped silica gel.

The phosphoric acid doped silica gel obtained in the above process waspulverized and was stirred in a toluene solution of (H-1). Here, theratio of the proton conducting solid electrolyte to the solid content ofthe (H-1) copolymer was chosen to be 19:1 by weight. The slurry thusobtained was applied onto a fluorocarbon resin plate by a doctor blademethod, and was dried by allowing the toluene to evaporate under areduced pressure at 100° C. After drying for three hours, the resultingsheet was separated from the fluoroplastic plate, to obtain the protonconducting molded solid electrolyte.

The ionic conductivity of the proton conducting molded solidelectrolyte, when measured by the same AC impedance method as used inEXAMPLE 1, was 3.2×10⁻³ S/cm.

In the bending test conducted in the same manner as in EXAMPLE 1, noexternally discernible faults were observed, thus demonstrating that theproton conducting molded solid electrolyte according to this example hadhigher flexibility.

In this way, it has been found that a proton conducting molded solidelectrolyte having high workability and high proton conductivity can beobtained according to the present invention using a proton conductinginorganic solid electrolyte and a hydrogenated block copolymer.

EXAMPLE 14

In this example, a silver ion conductive molded solid electrolyte wasproduced by using a solid electrolyte represented by Ag₆I₄WO₄ as thesilver ion conductive solid electrolyte and (H-1) as the hydrogenatedblock copolymer.

First, Ag₆I₄WO₄ was synthesized in the following manner.

Silver iodide (AgI), silver oxide (Ag₂O), and tungsten oxide (WO₃) wereused as starting materials. These starting materials were mixedtogether, and the mixture was heated and melted at 400° C. in a quartzcrucible. Thereafter, the mixture was allowed to cool in the furnace, toobtain the silver ion conductive solid electrolyte represented byAg₆I₄WO₄.

The silver ion conductive solid electrolyte obtained in the aboveprocess was pulverized and stirred in a toluene solution of (H-1). Here,the ratio of the silver ion conductive solid electrolyte to the solidcontent of the (H-1) copolymer was chosen to be 97:3 by weight. Theslurry thus obtained was applied onto a fluorocarbon resin plate by adoctor blade method, and was dried by allowing the toluene to evaporateunder a reduced pressure at 100° C. After drying for three hours, theresulting sheet was separated from the fluorocarbon resin plate, toobtain the silver ion conductive molded solid electrolyte.

The ionic conductivity of the silver ion conductive molded solidelectrolyte and, for comparison purposes, the ionic conductivity of thesilver ion conductive solid electrolyte before adding the hydrogenatedblock copolymer, were measured by the same AC impedance method as usedin EXAMPLE 1. The result showed that the ionic conductivity of thesilver ion conductive solid electrolyte itself was 4.0×10⁻² S/cm. On theother hand, after addition of the hydrogenated block copolymer, theionic conductivity was 2.3×10⁻² S/cm, the rate of decrease relative tothe former being held within one half.

In the bending test conducted in the same manner as in EXAMPLE 1, noexternally discernible faults were observed, thus demonstrating that thesilver ion conductive molded solid electrolyte according to this examplehad higher flexibility.

EXAMPLE 15

A molded electrode was obtained by using a lithiated cobalt oxiderepresented by LiCoO₂, which is an electron-lithium ion mixed conductor,as the material that exhibits an electrochemical oxidation reductionreaction in an electrolyte, and (H-1) as the hydrogenated blockcopolymer. The details are shown below.

First, LiCoO₂ was synthesized by measuring and mixing cobalt oxide(Co₃O₄) and lithium carbonate (Li₂CO₃) at a ratio of Co/Li=1, and bybaking the mixture at 900° C. in the atmosphere.

Using the thus obtained LiCoO₂ and (H-1), a molded electrode wasobtained in the following manner.

First, the LiCoO₂ obtained in the above process was pulverized to 350mesh or finer powder. A toluene solution of (H-1) was then added to thepowder of LiCoO₂, and thoroughly kneaded to obtain a slurry. The mixingratio of the solid content of the hydrogenated block copolymer to theLiCoO₂ powder, when kneading, was chosen to be 5:95 by weight. Theslurry thus obtained was applied onto a fluorocarbon resin plate by adoctor blade method, and was dried by allowing the toluene to evaporateunder a reduced pressure at 100° C. After drying for three hours, byseparating from the fluorocarbon resin plate and cutting out, a moldedelectrode with a diameter of 10 mm and a thickness of 0.2 mm wasobtained.

For comparison purposes, using a water dispersion ofpolytetrafluoroethylene (hereinafter designated PTFE) in place of thehydrogenated block copolymer used in this example, a molded electrodewas produced in like manner.

Further, for comparison purposes, a molded electrode was produced bypressure molding LiCoO₂ into the shape of a disk 10 mm in diameter and0.2 mm in thickness, without adding a binder such as a hydrogenatedblock copolymer.

The electrochemical properties of the thus obtained molded electrodeswere evaluated using the AC impedance method described below.

FIG. 1 shows in simplified form the construction of a measuringapparatus. In the figure, numeral 1 indicates a sample holder. Themolded electrode 2 was set into the holder by pressing and adheringagainst a lead terminal 3, thus forming a test electrode. This testelectrode was immersed into an electrolyte solution 4 in a container 7.The electrolyte solution was prepared by dissolving lithium phosphorushexafluoride (LiPF₆) in the solvent mixture, which was obtained bymixing propylene carbonate and dimethoxy ethane in the ratio of 1:1 byvolume, so as to provide a concentration of 1.0 M. A reference electrode5 and a counter electrode 6 were each from a metallic lithium foil, andwere immersed in the electrolyte solution. The measuring cell was thusformed. By applying an AC voltage of 10 mV to the measuring cell usingan impedance analyzer, the AC impedance was measured over the frequencyrange of 100 kH to 1 mHz.

The results showed that in the case of the molded electrode producedwithout adding a binder, the formability of the electrode was inferiorand, during the measurement, the electrode active material LiCoO₂ wasdropped off into the electrolyte solution, making it impossible tomeasure the impedance. Impedance spectra for the electrode producedusing the hydrogenated block copolymer of the present invention as thebinder and the electrode produced using the PTFE in the comparativeexample were shown in FIG. 2. As can be seen from the figure, it wasfound that the molded electrode obtained by using the designatedpolymers of the present invention as the binder exhibited a lowimpedance value and achieved a high electrode reactivity.

As described above, it has been found that a molded electrode having ahigh electrode reactivity and excellent formability can be obtainedaccording to the present invention.

EXAMPLE 16

Except that (H-1) used as the hydrogenated block copolymer in EXAMPLE 15was replaced by (H-2), a molded electrode was obtained in the samemanner as in EXAMPLE 15.

To evaluate the electrode characteristics of the molded electrode, theAC impedance was measured by the same method as used in EXAMPLE 15; theresults showed that the impedance at 10 mHz was 310Ω, which was lowerthan that of the molded electrode of the comparative example in EXAMPLE15 that used PTFE as the binder.

EXAMPLE 17

Except that (H-1) used as the hydrogenated block copolymer in EXAMPLE 15was replaced by (H-3), a molded electrode was obtained in the samemanner as in EXAMPLE 15.

To evaluate the electrode characteristics of the molded electrode, theAC impedance was measured by the same method as used in EXAMPLE 15; theresults showed that the impedance at 10 mHz was 270Ω, which was lowerthan that of the molded electrode of the comparative example in EXAMPLE15 that used PTFE as the binder.

EXAMPLE 18

Except that (H-1) used as the hydrogenated block copolymer in EXAMPLE 15was replaced by (H-4), a molded electrode was obtained in the samemanner as in EXAMPLE 15.

To evaluate the electrode characteristics of the molded electrode, theAC impedance was measured by the same method as used in EXAMPLE 15; theresults showed that the impedance at 10 mHz was 420Ω, which was lowerthan that of the molded electrode of the comparative example in EXAMPLE15 that used PTFE as the binder.

EXAMPLE 19

By using LiNiO₂ as the electron-lithium ion mixed conductor in place ofthe lithiated cobalt oxide represented by LiCoO₂ used in EXAMPLE 15, andusing (H-2) as the hydrogenated block copolymer as in EXAMPLE 16, amolded electrode was produced. The details are shown below.

First, LiNiO₂ was synthesized by mixing together nickel oxide (NiO) andlithium hydroxide, and by heating the mixture at 800° C. in theatmosphere.

Next, the LiNiO₂ obtained in the above process was pulverized to 350mesh or finer powder. Using this LiNiO₂ powder and a toluene solution of(H-2), the molded electrode was produced in the same manner as inEXAMPLE 15.

For comparison purposes, using a toluene solution of the block copolymerSEBS used in COMPARATIVE EXAMPLE 1 in place of the hydrogenated blockcopolymer used in the present example, a molded electrode was producedin like manner.

Further, for comparison purposes, a molded electrode was produced bypressure molding LiNiO₂ into the shape of a disk 10 mm in diameter and0.2 mm in thickness, without adding a binder such as the designatedpolymers.

The electrochemical properties of the thus obtained molded electrodeswere evaluated by the same AC impedance method as used in EXAMPLE 15.

The results showed that in the case of the molded electrode producedwithout adding a binder, the formability of the electrode was inferiorand, during the measurement, the electrode active material LiNiO₂ wasdropped off into the electrolyte solution, making it impossible tomeasure the impedance. The AC impedance of the electrode produced usingthe hydrogenated block copolymer of the present invention as the binderand that of the electrode produced using the SEBS in the comparativeexample were measured; the results showed that the impedance of themolded electrode produced using the hydrogenated block copolymer of thepresent invention as the binder was 450Ω at 10 mHz, whereas theimpedance of the molded electrode produced using the SEBS in thecomparative example was 740Ω, thus demonstrating that the moldedelectrode according to the present invention exhibited a lower impedanceand achieved a higher electrode reactivity.

As described above, it has been found that a molded electrode having ahigh electrode reactivity and excellent formability can be obtainedaccording to the present invention.

EXAMPLE 20

By using a lithiated manganese oxide represented by LiMn₂O₄ as thematerial that exhibits an electrochemical oxidation reduction reactionin a lithium ion conductive electrolyte and, as in EXAMPLE 16, using(H-2) as the hydrogenated block copolymer, a molded electrode wasproduced. The details are shown below.

LiMn₂O₄ was synthesized by mixing together lithium carbonate (Li₂CO₃)and manganese acetate (Mn(CH₃COO)₂), and by heating the mixture at 750°C. in the atmosphere.

Next, the LiMn₂O₄ obtained in the above process was pulverized to 350mesh or finer powder. This LiMn₂O₄ powder and graphite powder as theelectron conductive material were mixed at a ratio of 9:1 by weight.Further using a toluene solution of (H-2), the molded electrode wasproduced in the same manner as in EXAMPLE 15. Here, the mixing ratio ofthe solid content of the hydrogenated block copolymer to the LiMn₂O₄powder, when kneading, was chosen to be 5:95 by weight.

For comparison purposes, using a water dispersion of PTFE in place ofthe hydrogenated block copolymer used in this example, a moldedelectrode was produced in like manner.

Further, for comparison purposes, a molded electrode was produced bypressure molding the mixture of the LiMn₂O₄ powder and graphite into theshape of a disk 10 mm in diameter and 0.2 mm in thickness, withoutadding a binder such as a hydrogenated block copolymer.

The electrochemical properties of the thus obtained molded electrodeswere evaluated by the same AC impedance method as used in EXAMPLE 15.

The results showed that in the case of the molded electrode producedwithout adding a binder, the formability of the electrode was inferiorand, during the measurement, the electrode active material LiMn₂O₄ wascast off into the electrolyte solution, making it impossible to measurethe impedance. The AC impedance of the electrode produced using thehydrogenated block copolymer of the present invention as the binder andthat of the electrode produced using the PTFE in the comparative examplewere measured; the results showed that the impedance of the moldedelectrode produced using the hydrogenated block copolymer of the presentinvention as the binder was 570Ω at 10 mHz, whereas the impedance of themolded electrode using the PTFE in the comparative example was 810Ω,thus demonstrating that the molded electrode of the present inventionexhibited a lower impedance and achieved a higher electrode reactivity.

EXAMPLE 21

By using graphite fluoride as the material that exhibits anelectrochemical oxidation reduction reaction in a lithium ion conductiveelectrolyte and, as in EXAMPLE 16, using (H-2) as the hydrogenated blockcopolymer, a molded electrode was produced. The details are shown below.

Graphite fluoride was synthesized by heating graphite powder at 600° C.in a fluorine gas.

Except that the graphite fluoride obtained in the above process was usedin place of LiMn₂O₄, the molded electrode of the present invention andmolded electrodes for comparison purposes were formed and theirelectrochemical properties examined in the same manner as in EXAMPLE 20.

The results showed that in the case of the molded electrode producedwithout adding a binder, the formability of the electrode was inferiorand, during the measurement, the electrode active material of graphitefluoride was dropped off into the electrolyte solution, making itimpossible to measure the impedance. The AC impedance of the moldedelectrode produced using the hydrogenated block copolymer of the presentinvention as the binder and that of the molded electrode produced usingthe PTFE in the comparative example were measured; the results showedthat the impedance of the molded electrode produced using thehydrogenated block copolymer of the present invention as the binder was770Ω at 10 mHz, whereas the impedance of the molded electrode producedusing the PTFE in the comparative example was 890Ω, thus demonstratingthat the molded electrode of the present invention exhibited a lowerimpedance and achieved a higher electrode reactivity.

EXAMPLE 22

Except that in place of LiCoO₂, natural graphite was used as thematerial that exhibits an electrochemical oxidation reduction reactionin a lithium ion conductive electrolyte, a molded electrode was producedand the electrode characteristics were examined in the same manner as inEXAMPLE 16.

The results showed that in the case of the molded electrode producedwithout adding a binder, the formability of the electrode was inferiorand, during the measurement, the electrode active material of naturalgraphite was dropped off into the electrolyte solution, making itimpossible to measure the impedance. The AC impedance of the moldedelectrode produced using the hydrogenated block copolymer of the presentinvention as the binder and that of the molded electrode produced usingthe PTFE in the comparative example were measured; the results showedthat the impedance of the molded electrode produced using thehydrogenated block copolymer of the present invention as the binder was370Ω at 10 mHz, whereas the impedance of the molded electrode producedusing the PTFE in the comparative example was 520Ω, thus demonstratingthat the molded electrode of the present invention exhibited a lowerimpedance and achieved a higher electrode reactivity.

EXAMPLE 23

By using the LiCoO₂ obtained in EXAMPLE 15 as the electron-lithium ionmixed conductor, the amorphous solid electrolyte0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ obtained in EXAMPLE 5 as the lithium ionconductive inorganic solid electrolyte, and (H-2) as the hydrogenatedblock copolymer, a molded electrode was obtained. The details are shownbelow.

Using the solid electrolyte obtained in EXAMPLE 5, the LiCoO₂ obtainedin EXAMPLE 15, and the hydrogenated block copolymer (H-2), the moldedelectrode was produced in the following manner.

First, the solid electrolyte obtained in the above process waspulverized to 350 mesh or finer powder. The power of the solidelectrolyte, the powder of LiCoO₂, and a toluene solution of (H-2) werethoroughly kneaded to obtain a slurry. The mixing ratio of the solidcontent of the hydrogenated block copolymer, the solid electrolytepowder, and the LiCoO₂ powder, when kneading, were chosen to be 1:32:67by weight. The slurry thus obtained was applied onto a fluorocarbonresin plate by a doctor blade method, and was dried by allowing thetoluene to evaporate under a reduced pressure at 100° C. After dryingfor three hours, the resulting film was separated from the fluoroplasticplate, and cut out to obtain a molded electrode with a diameter of 10 mmand a thickness of 0.2 mm.

For comparison purposes, using a toluene solution of the SEBS used inCOMPARATIVE EXAMPLE 1 in place of the hydrogenated block copolymer usedin the present example, a molded electrode was produced in like manner.

Further, for comparison purposes, a molded electrode was produced bypressure molding the mixture of the LiCoO₂ and solid electrolyte intothe shape of a disk 10 mm in diameter and 0.2 mm in thickness, withoutadding a binder such as a hydrogenated block copolymer.

The electrochemical properties of the thus obtained molded electrodeswere evaluated using the AC impedance method described below.

In FIG. 3, a simplified form the construction of a measuring apparatusis shown. In the figure, numeral 11 indicates a hollow sample holdermade of polyethylene terephthalate. The molded electrode 12 was set intothe holder with a lead terminal 13 pressed and adhered to the moldedelectrode 12, thus forming a test electrode. This test electrode and acounter electrode 15 formed from a metallic lithium foil pressed againsta lead terminal 14 were integrally molded with the lithium ionconductive solid electrolyte 16 interposed therebetween, thus forming ameasuring cell. By applying an AC voltage of 10 mV to the measuring cellusing an impedance analyzer, the AC impedance was measured over thefrequency range of 100 kH to 1 mHz.

The resulting impedance spectra are shown in FIG. 3. As can be seen fromthe figure, when the hydrogenated block copolymer of the presentinvention was used as the binder, the impedance was lower than thatobtained when the SEBS was used as the binder, though the impedance washigher than that obtained when no binder was used; it was thus foundthat a molded electrode exhibiting a high electrode reactivity wasobtained.

Next, the formability of these molded electrodes was evaluated byconducting a drop test. In the drop test, each molded electrode wasdropped onto a marble plate from a height of 50 cm, and the condition ofthe molded electrode after dropping was observed.

The results showed that no faults were observed on the molded electrodesthat used the hydrogenated block copolymer of the present invention orthe SEBS as the binder, but that cracks were observed on the moldedelectrode that did not use any binder.

As described above, it has been found that a molded electrode having ahigh electrode reactivity and excellent formability can be obtainedaccording to the present invention.

EXAMPLE 24

By using the LiNiO2 obtained in EXAMPLE 19 as the electron-lithium ionmixed conductor, the amorphous solid electrolyte0.05Li₂O-0.60Li₂S-0.35SiS₂ obtained in EXAMPLE 6 as the lithium ionconductive inorganic solid electrolyte in place of the0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ obtained in EXAMPLE 5, and (H-1) as thehydrogenated block copolymer, a molded electrode was obtained. Thedetails are shown below.

Using the solid electrolyte obtained in EXAMPLE 6. the LiNiO₂ obtainedin EXAMPLE 19, and the hydrogenated block copolymer (H-1), the moldedelectrode was produced in the same manner as in EXAMPLE 23.

Further, for comparison purposes, using a toluene solution of SEBS inplace of the hydrogenated block copolymer used in the present example, amolded electrode was produced in like manner.

Also, for comparison purposes, without adding a binder such as ahydrogenated block copolymer, a molded electrode was produced bypressure molding the mixture of the LiNiO₂ and solid electrolyte intothe shape of a disk 10 mm in diameter and 0.2 mm in thickness.

The electrochemical properties of the thus obtained molded electrodeswere evaluated using the same AC impedance method as in EXAMPLE 23. Theresults showed that the impedance of the molded electrode that used thehydrogenated block copolymer of the present invention as the binder was3.3×10³Ω at 10 mHz. On the other hand, the impedance of the moldedelectrode that did not use any binder was 1.7×10³Ω, and the impedance ofthe molded electrode that used SEBS as the binder was 5.4×10³Ω. Whilethe molded electrode of the present example exhibited a higher valuethan the molded electrode that did not use any binder, it exhibited alower value than the molded electrode that used SEBS as the binder; itwas thus found that a molded electrode exhibiting a high electrodereactivity was obtained.

Next, when the formability of these molded electrodes was evaluatedusing the same method as in EXAMPLE 23, no faults were observed on themolded electrodes that used the hydrogenated block copolymer of thepresent invention or the SEBS as the binder, but cracks were observed onthe molded electrode that did not use any binder.

EXAMPLE 25

Except that the amorphous solid electrolyte 0.01Li₃PO₄-0.63Li₂S-0.36SiS₂used in EXAMPLE 23 as the lithium ion conductive inorganic solidelectrolyte was replaced by a crystalline lithium ion conductive solidelectrolyte represented by Li_(1.3)Al_(0.3)Ti_(1.7)(PO₄)₃, a moldedelectrode was produced in the same manner as in EXAMPLE 23. The detailsare shown below.

As the starting materials for the solid electrolyte, lithium carbonate,aluminum oxide, titanium oxide, and orthophosphoric acid were used.These starting materials were mixed together, and pressure molded intothe form of a pellet, which was then sintered for 24 hours at 1300° C.to obtain the crystalline lithium ion conductive inorganic solidelectrolyte represented by Li_(1.3)Al_(0.3)Ti_(1.7)(PO₄)₃.

Except that the solid electrolyte thus obtained was used in place of theamorphous solid electrolyte represented by 0.01Li₃PO₄-0.63Li₂S-0.36SiS₂,the molded electrode was produced in the same manner as in EXAMPLE 23.

Further, for comparison purposes, using a water dispersion of PTFE inplace of the hydrogenated block copolymer used in the present example, amolded electrode was produced in like manner.

The electrochemical properties of the thus obtained molded electrodeswere evaluated using the same AC impedance method as in EXAMPLE 23. Theresults showed that the impedance of the molded electrode that used thehydrogenated block copolymer was 2.8×10³Ω at 10 mHz, whereas theimpedance of the molded electrode that used PTFE was 4.8×10³Ω. From theabove results, it was found that the molded electrode that used thehydrogenated block copolymer of the present invention as the binderexhibited a lower impedance.

Next, when the formability of these molded electrodes was evaluatedusing the same method as in EXAMPLE 23, the results showed that nodamage was caused to the molded electrodes that used the hydrogenatedblock copolymer of the present invention or the PTFE as the binder.

As described above, it has been found that a molded electrode having ahigh electrode reactivity and excellent formability can be obtainedaccording to the present invention.

EXAMPLE 26

By using the lithiated cobalt oxide LiCoO₂ used in EXAMPLE 15 as theelectron-lithium ion mixed conductor and (H-2) as the hydrogenated blockcopolymer, and also using a polyethylene mesh as the structural member,a molded electrode was obtained. The details are shown below.

The slurry containing the LiCoO₂ and hydrogenated block copolymer wasobtained in the same manner as in EXAMPLE 15. Next, using a doctor blademethod, the slurry was charged into the openings in the polyethylenemesh having a porosity of 70%. After that, the mesh was dried byallowing the toluene to evaporate under a reduced pressure at 120° C.,thus obtaining the molded electrode.

When the AC impedance of the molded electrode was measured in the samemanner as in EXAMPLE 15, the molded electrode exhibited almost the sameimpedance as the molded electrode obtained in EXAMPLE 15.

Next, a bending test was conducted to examine the flexibility of themolded electrode and evaluate the formability. The bending test wascarried out by winding the molded electrode around a 40-mm diameterstainless steel rod and visually inspecting the condition of theelectrode. The result showed that no externally discernible faults wereobserved on the molded electrode of this example, thus demonstratingthat the electrode had high flexibility. On the other hand, when thesame bending test was conducted on the molded electrode obtained inEXAMPLE 15, cracks were caused on the electrode.

As described above, it has been found that a molded electrode havingparticularly high formability and high electrochemical reactivitycharacteristics is obtained according to the present invention using ahydrogenated block copolymer and a material that exhibits anelectrochemical oxidation reduction reaction in a lithium ion conductiveelectrolyte, and also using a structural member.

EXAMPLE 27

Except that the LiCoO₂ used in EXAMPLE 26 as the electron-lithium ionmixed conductor was replaced by the LiNiO₂ obtained in EXAMPLE 19, andthat the polyethylene mesh used in EXAMPLE 26 as the structural memberwas replaced by a stainless steel mesh as an electron conductingstructural member, while using (H-2) as the hydrogenated block copolymeras in EXAMPLE 26, a molded electrode was produced in the same manner asin EXAMPLE 26.

The AC impedance of the molded electrode, when measured in the samemanner as in EXAMPLE 15, was 390Ω. which was lower than the impedance ofthe molded electrode obtained in EXAMPLE 19.

Next, a bending test was conducted to examine the flexibility of themolded electrode and evaluate the formability. The bending test wascarried out by winding the molded electrode around a 40-mm diameterstainless steel rod and visually inspecting the condition of theelectrode. The result showed that no externally discernible faults wereobserved on the molded electrode of this example, thus demonstratingthat the electrode had high flexibility.

EXAMPLE 28

By using the molded electrode obtained in EXAMPLE 15 as the cathode andthe molded electrode obtained in EXAMPLE 22 as the anode, and alsousing, as the lithium ion conductive electrolyte, a lithium ionconductive electrolyte comprising a lithium phosphorus hexafluoride(LiPF₆) dissolved in a solvent mixture of propylene carbonate anddimethoxy ethane, a lithium cell was obtained. The details are shownbelow.

First, a molded cathode and an molded anode were obtained by cutting outthe molded electrode obtained in EXAMPLE 15 and the molded electrodeobtained in EXAMPLE 22, respectively.

The lithium ion conductive liquid electrolyte was prepared by mixingpropylene carbonate and dimethoxy ethane in ratio of 1:1 by volume, andby dissolving lithium phosphorus hexafluoride in the solvent mixture soas to provide a concentration of 1.0 M.

A lithium cell having the cross section shown in FIG. 5 was fabricatedby using the molded cathode, the molded anode, a porous polyethyleneseparator interposed therebetween, and the lithium ion conductiveelectrolyte. In FIG. 5, numeral 21 indicates the molded cathode disposedin the center of a cell case 24. On top of the molded cathode 21, theseparator 23 and the moldedd anode 22 were arranged, and the lithium ionconductive electrolyte was dropped thereon; after that, a cell lid 26was fitted to seal the entire construction with a gasket 25.

For comparison purposes, by replacing the molded cathode and moldedanode used in the present example with the molded cathode and moldedanode produced for comparison purposes in EXAMPLE 15 and EXAMPLE 22using PTFE as the binder, a lithium cell was fabricated.

Further, for comparison purposes, using a polymer solid electrolyte asthe binder in place of the hydrogenated block copolymer, a lithium cellwas fabricated in the following manner.

For the polymer solid electrolyte, a lithium perchlorate(LiClO₄)/polyethylene oxide (PEO) system was used. First, polyethyleneoxide (hereinafter designated PEO) was dissolved in acetonitrile, andthen LiClO₄ was dissolved. Here, the mixing ratio of PEO and LiClO₄ waschosen so that the ratio of the lithium in LiClO₄ to the oxygen in PEOwould become 1/50. Except that the thus prepared solution was used, thelithium cell was fabricated in the same manner as first described.

The lithium cells thus fabricated were charged up to 4.2 V with acurrent of 1 mA. After charging, the internal impedances of the cellswere measured by an AC impedance method (with an applied AC voltage of10 mV and an AC frequency of 1 Hz), after which a charge/discharge testwas conducted within a voltage range of 3.0 V to 4.2 V with a current of1 mA.

As the result of the testing, abnormality was observed in the chargecurve during cell charging for the lithium cell that used the polymersolid electrolyte. When the cell was disassembled to investigate thecause, neither the cathode nor the anode retained their original shape,with each electrode being swollen remarkably that the currentcollectivity of the active material was lost. This was presumablybecause the polymer solid electrolyte was dissolved in the electrolyteand the formability of the electrodes was lost.

For the lithium cell that used the hydrogenated block copolymer of thepresent invention as the binder and the lithium cell that used PTFE asthe binder, the cell internal impedances obtained from the above testand the discharge capacity for each charge/discharge cycle are shown inTable 5 and FIG. 6, respectively. In either lithium cell, there wasobserved no decrease in discharge capacity associated withcharge/discharge cycles, but it was shown that the lithium cell thatused the hydrogenated block copolymer of the present invention exhibiteda lower internal impedance and had a larger discharge capacity.

As described above, it has been found that according to the presentinvention, the formability of the electrodes can be improved withoutsignificantly impairing the internal ion conductivity of the cell, andthus a lithium cell exhibiting excellent cell characteristics can beobtained.

TABLE 5 Cell Internal Impedance (Ω) Uses hydrogenated block copolymer 62Uses PTFE 102

EXAMPLE 29

Except that the molded electrode obtained in EXAMPLE 16 was used as themolded cathode, a lithium cell according to the present invention wasfabricated and the characteristics thereof was evaluated in the samemanner as in EXAMPLE 28.

As the result, the lithium cell constructed by adding the hydrogenatedblock copolymer according to the present invention showed a dischargecapacity of 14 mAh or higher and an internal impedance of 64Ω, achievinga higher discharge capacity and lower internal impedance than thelithium cell constructed in EXAMPLE 28 for comparison purposes usingPTFE as the binder.

EXAMPLE 30

Except that the molded electrode obtained in EXAMPLE 19 was used as themolded cathode, a lithium cell according to the present invention wasfabricated and the characteristics thereof was evaluated in the samemanner as in EXAMPLE 28.

Further, for comparison purposes, a lithium cell was fabricated by usingas the cathode the molded electrode of the comparative example producedin EXAMPLE 19 using SEBS as the binder, and the cell characteristicswere evaluated.

As the result, the lithium cell constructed by adding the hydrogenatedblock copolymer according to the present invention showed a dischargecapacity of 18 mAh and an internal impedance of 87Ω. On the other hand,the lithium cell of the comparative example constructed using SEBS asthe binder showed a discharge capacity of 16 mAh and an internalimpedance of 98Ω, and thus the lithium cell of the present inventionshowed a higher discharge capacity and lower internal impedance.

EXAMPLE 31

By using a molded electrode produced in the same manner as in EXAMPLE 15except that titanium disulfide represented by TiS₂ was used as thecathode active material in place of the lithiated cobalt oxiderepresented by LiCoO₂, and also using metallic lithium as the anodeactive material in place of the natural graphite used in EXAMPLE 29, alithium cell was fabricated. The details are shown below.

First, TiS₂ was synthesized by a CVD process from metallic titanium andsulfur.

Next, the TiS₂ obtained in the above process was pulverized to 350 meshor finer powder. Using this TiS₂ powder in place of the LiCoO₂ powder,the molded electrode was produced in the same manner as in EXAMPLE 15.Except that the molded electrode obtained in the above process was usedfor the cathode and the metallic lithium foil for the anode, the lithiumcell according to the present invention was fabricated in the samemanner as in EXAMPLE 29. For comparison purposes, a lithium cell wasfabricated by using PTFE in place of the hydrogenated block copolymer(H-1).

The lithium cells thus fabricated were discharged down to 1.8 V with acurrent of 500 μA. After discharging, the internal impedances of thecells were measured by an AC impedance method (with an applied ACvoltage of 10 mV and an AC frequency of 1 Hz), after which acharge/discharge test was conducted within a voltage range of 1.8 V to2.8 V with a current of 500 μA.

As the result, the lithium cell that used the hydrogenated blockcopolymer of the present invention showed a discharge electricalquantity of 28 mAh and an internal impedance of 74Ω. On the other hand,the cell that used PTFE showed a discharge electrical quantity of 23 mAhand an internal impedance of 86Ω. From these results, it was found thatthe cell of the present invention had a lower internal impedance andlarger discharge capacity.

EXAMPLE 32

Except that the molded electrode obtained in EXAMPLE 20 was used as thecathode, a lithium cell was fabricated in the same manner as in EXAMPLE29.

For comparison purposes, except that the molded electrode of thecomparative example produced in EXAMPLE 16 using PTFE as the binder wasused as the cathode, a lithium cell was fabricated and itscharacteristics evaluated in the same manner as above.

As the result, the lithium cell that used the hydrogenated blockcopolymer of the present invention showed a discharge capacity of 11 mAhand an internal impedance of 230Ω. On the other hand, the cell that usedPTFE showed a discharge capacity of 8.5 mAh and an internal impedance of340Ω. From these results, it was found that the cell of the presentinvention had a lower internal impedance and larger discharge capacity.

EXAMPLE 33

Except that an electrolyte comprising LiClO₄ dissolved in a solventmixture of propylene carbonate and dimethoxy ethane was used as thelithium ion conductive electrolyte, a lithium cell according to thepresent invention and a lithium cell for comparison purposes werefabricated in the same manner as in EXAMPLE 29.

As the result, the discharge capacity and internal impedance of thelithium cell that used the hydrogenated block copolymer of the presentinvention were 13 mAh and 67Ω, respectively, whereas those for the cellthat used PTFE were 11 mAh and 71Ω, respectively.

EXAMPLE 34

Except that the molded electrode produced in EXAMPLE 27 using thestainless steel mesh for increased formability of the electrode was usedas the cathode, and that an molded anode using a stainless steel mesh,hereinafter described, was used as the anode, a lithium cell wasfabricated in the same manner as in EXAMPLE 28.

The molded anode was produced by charging the slurry containing naturalgraphite and (H-2), obtained in EXAMPLE 22, into a stainless steel mesh,and by allowing the toluene to evaporate under a reduced pressure at100° C.

Using the thus produced molded anode and the molded electrode obtainedin EXAMPLE 27 as the cathode, the lithium cell was fabricated in thesame manner as in EXAMPLE 28.

When the characteristics of the thus fabricated lithium cell wereevaluated in the same manner as in EXAMPLE 28, there was observed nodecrease in discharge capacity associated with charge/discharge cycles,and the discharge capacity and internal impedance of the lithium cellthat used the structural member obtained in the present example were 17mAh and 51Ω, respectively, showing that the cell fabricated in thisexample had a lower internal impedance and larger discharge capacity.

EXAMPLE 35

In EXAMPLES 28 to 34, there were explained the examples wherein alithium cell was constructed as the electrochemical device, but in thisexample, an example wherein a nickel-cadmium cell was constructed as theelectrochemical device.

First, a molded electrode used for the anode was produced in thefollowing manner.

A powder of cadmium oxide and a toluene solution of the hydrogenatedblock copolymer (H-2) were mixed together by maintaining the ratio ofthe cadmium oxide to the copolymer at 95:5 by weight. The slurry thusprepared was applied on and charged in a nickel plated iron punchingmetal as an electron conductive structural member, and the toluene wasevaporated at 100° C. to obtain the molded electrode.

Next, a molded electrode used for the cathode was produced in thefollowing manner.

Nickel hydroxide, metallic cobalt powder, and a toluene solution of(H-2) were mixed together to produce a mixture of the nickel hydroxide,metallic cobalt, and copolymer in proportions of 90:5:5 by weight. Theslurry thus prepared was charged into a nickel foam as an electronconductive structural member, and the toluene was evaporated at 100° C.to obtain the molded electrode.

By using the thus obtained cathode and anode, and also using a polyamidefiber unwoven fabric as the separator and a 7N KOH aqueous solution asthe electrolyte, The nickel-cadmium cell was fabricated.

When the charge/discharge performance and rate characteristics of thethus fabricated nickel-cadmium cell were examined, the results werecomparable to those of conventional cells.

As described above, it has been found that the hydrogenated blockcopolymer is also applicable as a binder for electrochemical devicesusing liquid electrolyte.

EXAMPLE 36

By using (H-1) as the hydrogenated block copolymer, a lithiated cobaltoxide represented by LiCoO₂ as the cathode active material, indium asthe anode active material, and an amorphous solid electrolyterepresented by 0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ as the lithium ionconductive electrolyte, an all-solid lithium cell was obtained. Thedetails are shown below.

The lithium ion conductive solid electrolyte used here was the same asthat obtained in EXAMPLE 5, and LiCoO₂ was the same as that obtained inEXAMPLE 15. Further, the same molded solid electrolyte as obtained inEXAMPLE 5 and the same molded electrode as obtained in EXAMPLE 23 wereused here.

Using the lithium ion conductive solid electrolyte, LiCoO₂, and moldedelectrode described above, the all-solid lithium cell was fabricated inthe following manner.

First, for comparison purposes, a solid electrolyte layer and a cathodelayer were formed by a powder molding method using a lithium ionconductive solid electrolyte and a cathode material, neither containinga hydrogenated block copolymer, and an all-solid lithium cell A havingthe cross section shown in FIG. 7 was thus fabricated. In FIG. 7,numeral 31 indicates the cathode, 33 the lithium ion conductive solidelectrolyte layer, and 32 the anode formed from a metallic indium foil;these constituent elements were integrally pressure molded. Theintegrally pressure molded pellet was placed in a stainless steel cellcase 34, and was sealed therein by fitting a stainless steel lid 36 withan insulating gasket 35.

Next, except that the above lithium ion conductive solid electrolytepowder was replaced by the lithium ion conductive molded solidelectrolyte obtained in EXAMPLE 5, a lithium cell B according to thepresent invention was fabricated in the same manner as above.

Further, except that the cathode used in the lithium cell A was replacedby the molded electrode obtained in EXAMPLE 23, a lithium cell Caccording to the present invention was fabricated in the same manner asthe lithium cell A.

Further, except that the lithium ion conductive solid electrolyte powderand the cathode material used in the lithium cell A were replaced by thelithium ion conductive molded solid electrolyte and the moldedelectrode, respectively, a lithium cell D according to the presentinvention was fabricated in the same manner as the lithium cell A.

Next, for comparison purposes, by using an isoprene-styrene randomcopolymer in place of the hydrogenated block copolymer used in thepresent example, and also using the molded solid electrolyte obtained inthe same manner as in EXAMPLE 5 and/or the molded electrode obtained inthe same manner as in EXAMPLE 23, a lithium cell E (with its solidelectrolyte layer formed from the molded solid electrolyte), a lithiumcell F (with its cathode layer formed from the molded electrode), and alithium cell G (with its solid electrolyte layer and cathode layerformed from the molded solid electrolyte and the molded electrode,respectively) were fabricated in like manner.

The lithium cells thus fabricated were charged up to 3.7 V with acurrent of 300 μA. After charging, the internal impedances of the cellswere measured by an AC impedance method (with an applied AC voltage of10 mV and an AC frequency of 1 Hz), after which a charge/discharge testwas conducted within a voltage range of 2.0 V to 3.8 V with a current of300 μA.

The internal impedances measured on the respective cells and thedischarge capacity for each charge/discharge cycle are shown in Table 6and FIG. 8, respectively. For the lithium cells B, C, and D according tothe present invention, there was observed almost no decrease indischarge capacity associated with charge/discharge cycles, though theinternal impedance was higher than that of the lithium cell A. On theother hand, in the case of the lithium battery A fabricated withoutadding the hydrogenated block copolymer, the decrease in capacityassociated with charge/discharge cycles was particularly noticeable.When the cross section thereof was observed by an X-ray CT toinvestigate the cause, cracks were observed on the pellet inside thecell, and it is regarded that the capacity dropped presumably because ofthe deterioration of the cell internal bonding condition caused byelectrode volumetric changes associated with charging and dischargingoperations.

In the case of the lithium cells E, F, and G that used theisoprene-styrene random copolymer as the binder for the solidelectrolyte layer and/or the molded electrode, their internal impedancesafter charging showed large values, and their discharge capacities weresmall though the decrease associated with charge/discharge cycles wassmall. This was presumably because the added polymers interfered withthe internal ion conductivity of the cell, as a result of which theinternal impedance of the cell increased, increasing the overvoltageduring discharging and thus decreasing the discharge capacity.

As described above, it has been found that according to the presentinvention, an all-solid lithium cell can be obtained that achievesexcellent charge/discharge cycle characteristics by preventing thedeterioration of the cell internal bonding property associated withelectrode volumetric changes during charging and discharging operations,without significantly impairing the internal ion conductivity of thecell.

TABLE 6 Internal impedance (Ω) Cell A 340 Cell B 470 Cell C 610 Cell D740 Cell E 2500 Cell F 3100 Cell G 3800

EXAMPLE 37

Except that the molded electrode used in EXAMPLE 36 as the cathode wasreplaced by the molded electrode obtained in EXAMPLE 24, and that themolded solid electrolyte used in EXAMPLE 36 as the solid electrolytelayer was replaced by the molded solid electrolyte obtained in EXAMPLE6, an all-solid lithium cell I (with its solid electrolyte layer formedfrom the molded solid electrolyte), lithium cell J (with its cathodelayer formed from the molded electrode), and lithium cell K (with itssolid electrolyte layer and cathode layer formed from the molded solidelectrolyte and the molded electrode, respectively) according to thepresent invention were fabricated and their characteristics evaluated inthe same manner as in EXAMPLE 36.

Further, without using a hydrogenated block copolymer for either layer,an all-solid lithium cell H was fabricated in which the solidelectrolyte layer and the cathode layer were formed by a powder moldingmethod using an electrolyte and a cathode material.

For comparison purposes, by using as the molded electrode the moldedelectrode of the comparative example produced in EXAMPLE 24 using SEBSas the binder, and using a molded solid electrolyte containing 3.5% byweight of SEBS, an all-solid lithium cell L (with its solid electrolytelayer formed from the molded solid electrolyte), lithium cell M (withits cathode layer formed from the molded electrode), and lithium cell N(with its solid electrolyte layer and cathode layer formed from themolded solid electrolyte and the molded electrode, respectively) werefabricated.

As can be seen from the results shown in Table 7, for the lithium cellsI, J, and K according to the present invention, there was observedalmost no decrease in discharge capacity associated withcharge/discharge cycles, though the internal impedance was higher thanthat of the lithium cell H. On the other hand, in the case of thelithium battery H fabricated without adding the hydrogenated blockcopolymer, the decrease in capacity associated with charge/dischargecycles was particularly noticeable. When the cross section thereof wasobserved by an X-ray CT to investigate the cause, cracks were observedon the pellet inside the cell, and the capacity dropped presumablybecause of the deterioration of the cell internal bonding conditioncaused by electrode volumetric changes associated with charging anddischarging operations. In the case of the lithium cells L, M, and Nthat used SEBS, their internal impedances after charging showed largevalues, and their discharge capacities were small though the decreaseassociated with charge/discharge cycles was small. This was presumablybecause the added polymers interfered with the internal ion conductivityof the cell, as a result of which the internal impedance of the cellincreased, increasing the overvoltage during discharging and thusdecreasing the discharge capacity.

TABLE 7 Internal impedance (Ω) Cell H 430 Cell I 570 Cell J 690 Cell K800 Cell L 2800 Cell M 3300 Cell N 3900

EXAMPLE 38

By using the titanium disulfide represented by TiS₂ obtained in EXAMPLE31 as the cathode active material in place of the lithiated cobalt oxiderepresented by LiCoO₂ used in EXAMPLE 36, metallic lithium as the anodeactive material in place of the indium used in EXAMPLE 36, and (H-2) asthe hydrogenated block copolymer, an all-solid lithium cell wasfabricated. The details are shown below.

First, the TiS₂ obtained in EXAMPLE 31 was pulverized to 350 mesh orfiner powder. Except that this TiS₂ powder was used in place of theLiCoO₂ powder, the molded electrode was produced in the same manner asin EXAMPLE 23. By using the molded electrode and metallic lithium foil,the lithium cell according to the present invention was fabricated. Forcomparison purposes, a lithium cell that did not use any hydrogenatedblock copolymer and a lithium cell that used SEBS in place of thehydrogenated block copolymer were also fabricated.

The lithium cells thus fabricated were discharged down to 1.8 V with acurrent of 100 μA. After discharging, the internal impedances of thecells were measured by an AC impedance method (with an applied ACvoltage of 10 mV and an AC frequency of 1 Hz), after which acharge/discharge test was conducted within a voltage range of 1.8 V to2.8 V with a current of 100 μA.

As the result, while the lithium cell of the present invention in whichthe hydrogenated block copolymer was added to either the solidelectrolyte layer or the cathode layer showed a slightly higher internalimpedance than the lithium cell fabricated without adding anyhydrogenated block copolymer, the internal impedance was held to 1 k Ωor lower, and there was observed almost no decrease in dischargecapacity associated with charge/discharge cycles. In the case of thelithium cell that used SEBS as the binder, on the other hand, theinternal impedance after charging showed 2 k Ω or higher value.Furthermore, though the decrease associated with charge/discharge cycleswas small, the discharge capacity was also small.

EXAMPLE 39

Except that for the cathode the lithiated manganese oxide represented byLiMn₂O₄ obtained in EXAMPLE 20 was used in place of the lithiated cobaltoxide represented by LiCoO₂ used in EXAMPLE 36, an all-solid lithiumcell was fabricated in the same manner as in EXAMPLE 36. The details areshown below.

First, the LiMn₂O₄ obtained in EXAMPLE 20 was pulverized to 350 mesh orfiner powder. The cathode material was prepared by mixing the LiMn₂O₄powder, the solid electrolyte powder obtained in EXAMPLE 5, and graphitepowder as an electron conductive material in proportions of 6:3:1 byweight.

Except that the above cathode material was used, and using the thusproduced molded electrode, the lithium cell was fabricated, the moldedelectrode was produced in the same manner as in EXAMPLE 23.

For comparison purposes, a lithium cell that did not use anyhydrogenated block copolymer and a lithium cell that used SEBS in placeof the hydrogenated block copolymer were fabricated and theircharacteristics were evaluated.

As the result, while the lithium cell of the present invention in whichthe hydrogenated block copolymer was added to either the solidelectrolyte layer or the cathode layer showed a slightly higher internalimpedance than the lithium cell fabricated without adding anyhydrogenated block copolymer, the internal impedance was held to 1 k Ωor lower, and there was observed almost no decrease in dischargecapacity associated with charge/discharge cycles. In the case of thelithium cell that used SEBS, on the other hand, the internal impedanceafter charging showed 2 k Ω or higher value, and though the decreaseassociated with charge/discharge cycles was small, the dischargecapacity was also small.

EXAMPLE 40

Except that a molded electrode formed from natural graphite was used asthe anode material in place of the indium used in EXAMPLE 36, anall-solid lithium cell according to the present invention was fabricatedin the same manner as in EXAMPLE 36. The details are shown below.

The anode material was prepared by mixing natural graphite and thelithium ion conductive solid electrolyte obtained in EXAMPLE 36 inproportions of 9:1 by weight. Using this anode material, the moldedelectrode was produced in the same manner as in EXAMPLE 23.

Using the molded anode thus produced, the molded cathode obtained inEXAMPLE 23, and the lithium ion conductive molded solid electrolyteobtained in EXAMPLE 5, the lithium cell was fabricated in the samemanner as in EXAMPLE 36.

For comparison purposes, a lithium cell was fabricated without adding ahydrogenated block copolymer.

The lithium cells thus fabricated were charged up to 4.2 V with acurrent of 300 μA. After charging, the internal impedances of the cellswere measured by an AC impedance method (with an applied AC voltage of10 mV and an AC frequency of 1 Hz), after which a charge/discharge testwas conducted within a voltage range of 2.5 V to 4.2 V with a current of300 μA.

As the result, while the lithium cell of the present inventionfabricated by adding the hydrogenated block copolymer showed a slightlyhigher internal impedance than the lithium cell fabricated withoutadding any hydrogenated block copolymer, the internal impedance was heldto 1 k Ω or lower, and there was observed almost no decrease indischarge capacity associated with charge/discharge cycles.

EXAMPLE 41

By using the same cathode material, anode material, and electrolyte asused in the lithium cell C in EXAMPLE 36, and also using a stainlesssteel mesh to improve the formability of the cathode, a lithium cell wasfabricated.

First, a slurry was prepared that contained LiCoO₂ and0.01Li₃PO₄-0.63Li₂S-0.36SiS₂ used in EXAMPLE 36 as the cathode activematerial and solid electrolyte and (H-2) as the hydrogenated blockcopolymer. Next, using a doctor blade method, the slurry was chargedinto the openings in the stainless steel mesh having a porosity of 80%and serving as the structural member. After that, the mesh was dried byallowing the toluene to evaporate under a reduced pressure at 100° C.Thereafter, it was cut out into the shape of a disk 16 mm in diameter,to produce the molded cathode.

Using the thus produced molded cathode, the lithium cell was fabricatedin the same manner as the lithium cell C in EXAMPLE 36.

When the characteristics of the thus fabricated lithium cell wereevaluated in the same manner as in EXAMPLE 36, there was observed nodecrease in discharge capacity associated with charge/discharge cycles;further, the internal impedance of the lithium cell fabricated using thestructural member obtained in the present example was 480Ω, which waslower than the internal impedance of the lithium cell C likewisefabricated using the molded cathode in EXAMPLE 36. It was also foundthat the discharge capacity was 14 mAh which was larger than the lithiumcell C.

As described above, it has been found that according to the presentinvention, a lithium cell having superior cell characteristics can beobtained by improving the formability of the electrode and inserting astructural member in the electrode, without significantly impairing theinternal ion conductivity of the cell.

EXAMPLE 42

In this example, there is explained an example in which anelectroluminescent display device was fabricated as an all-solidelectrochemical device by using the proton conducting solid electrolyteobtained in EXAMPLE 13.

A thin film of tungsten oxide (WO₃) was used as a display electrode ofthe electroluminescent display device. As shown in FIG. 9, the tungstenoxide thin film 43 was formed by an electron beam deposition method on aglass substrate 41 on whose surface an ITO layer 42 had been formed as atransparent electrode by a sputtering deposition method.

A thin film of tungsten oxide (H_(x)WO₃) doped with proton, formed inthe following manner, was used as the counter electrode.

First, in the same manner as the above display electrode, a tungstenoxide thin film was formed on a glass substrate 45 on whose surface anITO electrode 46 had been formed. This glass substrate was immersed Inan aqueous solution of chloroplatinic acid (H₂PtCl₆), and then dried ina hydrogen stream, to reduce the tungsten oxide to tungsten bronze(H_(x)WO₃) 47.

The electrolyte layer of the electroluminescent display device wasformed in the following manner.

First, a toluene solution of (H-1) was added to the phosphoric aciddoped silica gel obtained in EXAMPLE 13. Further, since the electrolytelayer was also used as a reflector, 5% alumina powder by weight wasadded to the silica gel to color the electrolyte layer white. Theresulting mixture was then kneaded until the mizture turned into aslurry, and using a doctor blade method, the slurry was applied to athickness of 50 μm on the surface of the previously formed displayelectrode, thus forming the electrolyte layer.

On the display electrode on whose surface the electrolyte layer wasformed in the above manner, the earlier produced counter electrode wasplaced in such a manner as to cover the electrolyte layer, and thesolvent was evaporated under a reduced pressure. The resulting crosssection is shown in FIG. 10. Further, an ultraviolet curing resin 50 wasapplied to seal and adhere the end faces, thus completing thefabrication of the electroluminescent display device. In FIG. 10,numeral 44 designates the display electrode, 48 the counter electrode,49 the electrolyte layer, and 51 and 52 are lead terminals.

The thus fabricated electroluminescent display device was subjected toan operation cycle test in which a voltage of −1 V was applied for twoseconds to the display electrode relative to the counter electrode tocolor the display electrode, and then a voltage of +1 V was applied fortwo seconds to extinguish the color. The results after 10,000 cyclesshowed no performance degradation, retaining the ability to produce andextinguish color.

As described above, it has been found that an electroluminescent displaydevice having excellent operation cycle characteristics can be obtainedaccording to the present invention.

In the above EXAMPLES, there are explained the cases that lithium ionconductive amorphous solid electrolytes such as 0.6Li₂S-0.4SiS₂,0,01Li₃PO₄-0.63Li₂S-0.36SiS₂, 0.5Li₂S-0.5P₂S₅, and 0.6Li₂S-0.4B₂S₃ wereused for the lithium ion conductive inorganic solid electrolyte.However, it will be appreciated that similar effects can also beobtained by using the solid electrolytes with different compositionratios than those given above, electrolytes containing other sulfidessuch as Li₂S-GeS₂ not described in the EXAMPLES, electrolytes containingother lithium halides such as LiCl-Li₂S-SiS₂ and LiBr-Li₂S-P₂S₅,electrolytes of pseudoquaternary systems such as LiL-Li₂S-SiS₂-P₂S₅ andLiI-Li₃PO₄-Li₂S-SiS₂, or other crystalline lithium ion conductiveinorganic solid electrolytes such as Li₃N,Li_(1.3)Sc_(0.3)Ti_(1.7)(PO₄)₃, and Li_(0.2)La_(0.6)TiO₃ not describedin the EXAMPLES; thus, the lithium ion conductive solid electrolyte ofthe present invention is not limited to those described in the EXAMPLES.

Further, the EXAMPLES so far described have dealt with lithiated cobaltoxides, lithiated nickel oxides, lithiated manganese oxides, andgraphite fluorides as examples of the substance that exhibits anelectrochemical oxidation reduction reaction in a lithium ion conductiveelectrolyte; however, it will be appreciated that similar effects canalso be obtained by using other substances, such as copper oxides andiron sulfides, that exhibit an electrochemical oxidation reductionreaction in a lithium ion conductive electrolyte, and the presentinvention is not limited to those described in the EXAMPLES as thesubstance that exhibits an electrochemical oxidation reduction reactionin a lithium ion conductive electrolyte.

In some EXAMPLES, lithium cells were described that used as the lithiumion conductive electrolyte an electrolyte comprising LiPF6 or LiClO₄dissolved in a solvent mixture of propylene carbonate and dimethoxyethane; however, it will be appreciated that similar effects can also beobtained by using an electrolyte that uses other supporting salts suchas LiBF₄ not described in the EXAMPLES or an electrolyte that uses othersolvents such as ethylene carbonate not described in the EXAMPLES, andthe present invention is not limited to the lithium cells that use theelectrolytes described in these EXAMPLES.

Further, in the EXAMPLES, the electronically insulating structuralmember has only been described as comprising a polyethylene mesh or aglass fiber mesh; however, it will be appreciated that similar effectscan also be obtained by using meshes of other materials such aspolypropylene, polyester, or cellulose, or even by using non-wovenfabrics of such materials instead of meshes, and the electronicallyinsulating structural member of the present invention is not limited tothe polyethylene mesh or the glass fiber mesh.

Likewise, in the EXAMPLES, the electron conductive structural member hasonly been described as comprising a stainless steel mesh; however, itwill be appreciated that similar effects can also be obtained by usingmeshes of other materials such as titanium, or even by using non-wovenfabrics of such materials instead of meshes, and the structural memberof the present invention is not limited to those described in theEXAMPLES.

Industrial Applicability

As described above, according to the present invention, a molded solidelectrolyte having a high ionic conductivity as well as high formabilityor a molded electrode having high electrode activity can be obtained;furthermore, by using the molded solid electrolyte or the moldedelectrode, an electrochemical device exhibiting excellent operatingcharacteristics can be obtained.

What is claimed is:
 1. A molded solid electrolyte comprising a solidelectrolyte and a hydrogenated block copolymer obtained by hydrogenatinga straight chain or branched block copolymer; the straight chain orbranched block copolymer containing, a block (A) comprisingpolybutadiene of which 1,2-vinyl bond content is 15% or less and a block(B) comprising a butadiene (copolymer consisting of 50 to 100% by weightof butadiene and 0 to 50% by weight of other monomers in which 1,2-vinylbond content of butadiene portion is 20 to 90%, wherein (A)/(B)=5 to70/95 to 30% by weight.
 2. The molded solid electrolyte in accordancewith claim 1, wherein the solid electrolyte is a lithium ion conductivesolid electrolyte.
 3. The molded solid electrolyte in accordance withclaim 1, wherein the solid electrolyte is an amorphous solidelectrolyte.
 4. The molded solid electrolyte in accordance with claim 3,wherein the amorphous solid electrolyte is a lithium ion conductivesolid electrolyte.
 5. The molded solid electrolyte in accordance withclaim 4, wherein the lithium ion conductive amorphous solid electrolyteconsists essentially of a sulfide.
 6. The molded solid electrolyte inaccordance with claim 5, wherein the lithium ion conductive amorphoussolid electrolyte contains silicon.
 7. The molded solid electrolyte inaccordance with claim 1, which includs an electronically insulatingstructural member.
 8. A molded electrode consisting essentially of anelectrode active material and a hydrogenated block copolymer obtained byhydrogenating a straight chain or branched block copolymer; the straightchain or branched block copolymer containing a block (A) comprisingpolybutadiene whose 1,2-vinyl bond content is 15% or less and a block(B) comprising a butadiene (co)polymer consisting of 50 to 100% byweight of butadiene and 0 to 50% by weight of other monomers in which1,2-vinyl bond content of butadiene portion is 20 to 90%. wherein(A)/(B)=5 to 70/95 to 30% by weight.
 9. The molded electrode inaccordance with claim 8, which contains a lithium ion conductive solidelectrolyte.
 10. The molded electrode in accordance with claim 9,wherein the lithium ion conductive solid electrolyte is an amorphoussolid electrolyte consisting essentially of a sulfide.
 11. The moldedelectrode in accordance with claim 8, which contains a structuralmember.
 12. The molded electrode in accordance with claim 11, whereinthe structural member is an electronically insulating structural member.13. An electrochemical device comprising a pair of electrodes and anelectrolyte layer, wherein at least either the pair of electrodes or theelectrolyte layer contains a hydrogenated block copolymer obtained byhydrogenating a straight chain or branched block copolymer containing ablock (A) comprising polybutadiene whose 1,2-vinyl bond content is 15%or less and a block (B) comprising a butadiene (co)polymer consisting of50 to 100% by weight of butadiene and 0 to 50% by weight of othermonomers in which 1,2-vinyl bond content of butadiene portion is 20 to90%, wherein (A)/(B)=5 to 70/95 to 30% by weight.